Well, I think it important to recognize that "Isekai" as in "Otherworld" has a very long presence and history, as you point out, but also in anime.
For example,
Inuyasha is basically an isekai. There are also more modern ones, such as
Familiar of Zero, which has quite a few tropes that are evident in the current isekai fad, though not as badly handled. (Wow, citing Familiar of Zero as a good isekai does show how badly the genre has fallen). I actually tend to feel that Sword Art Online is not really the jumping off point for modern Isekai, but rather for a specific element of an overpowered hero who has no difficulty pwning every obstacle in his way. That probably has shown up in other genres as well, not just isekai, it's just that modern isekai tend to be really prevalent with it. Mainly because (as has been pointed out) most of these isekai are self-published web novels that happened to become popular. Thus they tend to have a lot of the same problems as fantasy novels written by teenage DnD fans.
I don't mind criticizing the modern isekai, but I think it is important to not slander the whole genre. It would sort of be like reading Eragon and thus declaring most of high fantasy stories to be trash.
I think a better approach is to consider what are some specific things that are a problem with many modern isekai, and what are some specific interesting variations that could be written. Since so many of the authors are teenagers writing on the internet, it's actually possible that criticism on a forum might end up having an impact.
I would identify some the main common isekai problems as follows:
1: The lack of concern about returning to their own world and family. One of the major elements of most traditional isekai stories is that the protagonists return to their own world, changed by the experience. The lack of this element is a major problem with most isekai, because it removes one of the driving causes of character development. A few can get around this, such as Re:Zero, by putting other obstacles in place that drive character development. So I wouldn't say this is a hard rule, that a quest to return home be included, but if an author decides to leave it out, they have to think hard about what the internal conflict will be that drives the character development. Thus, the current trend of killing the main character is not a great method for putting them in another world. Originally it was a homage to
Yu Yu Hakusho, (Konosuba in particular was parodying this), but consider how very enlightening his death was for Yusuke compared to how it has hardly any emotional impact on modern isekai characters. Not to mention the entire first arc of Yu Yu Hakusho was about Yusuke trying to return to life.
2: Granting the main hero an ability that makes it so he succeeds without struggle. While there can be some interest in how an overpowered character acts, it again removes a major source of character development. Plus it gets boring very quickly. Granting the protagonist an ability is okay, but I think it would be much more interesting to take an average person, and stick them in a fantasy world without gaining any powers. Forcing them to try and find a different way to survive. Of course, granting an ability can be okay, as long as there is some major effort required by the character. For example, a character that was reborn as a child, but retained memories of a previous life and decided to put more effort into his life. Rather than appealing to someone who wants power without working hard, it would suggest the need for changing one's character to succeed. Other elements that have the same problem are modeling the new world on a game world, with various level abilities, and other such user interfaces allowing a protagonist to avoid the difficulties expected with arriving in a new world.
3: Treating the characters around the protagonist as existing to serve the needs of the protagonist. Not giving these other characters their own backgrounds, motivations, and values creates a boring world were the protagonist doesn't have conflict with or difficulty persuading others around him.
Basically, it all becomes summed up by the way too many current isekai remove sources of conflict. This makes the story uninteresting, and limits or eliminates character development. Perhaps you can get away with doing a few things that eliminate certain types of conflict (such as a universal translator) and then focus on the other conflicts that remain. Avoid conflict altogether however, has problems as a story. Unless you intend to just tell a slice of life story in another world, which I suppose could be interesting, but begs the question of why put a person from this world in a new world? It would be better to tell a slice of life story with characters that originate in the other world.
Some ideas that come from this that could make an isekai more interesting:
1: A story of a "hero" summoned to another world who resents being essentially kidnapped and sent off to fight some demon lord. There are a few isekai stories that have done this but none very well. Rising of the Shield Hero is the closest, but that involves other major aspects to the story that take away from the aspect that summoning a hero is not a nice thing to do.
2a: A story of a person trapped in another world via a portal or something, but without all the infrastructure of people. Essentially more of a survival story set in a fantasy world. This would have elements of how dependent we are on modern technology, and how difficult survival can be. You might even deny the protagonist magic, so he basically has to survive in a magic world without magic. Something like
Primitive Technology, only with much more dire problems if the protagonist fails. The ulimate goal is to figure out how to reactivate the portal and get home.
2b: A story of a person trapped in another world, in which the protagonist doesn't have magic, but they do have their knowledge of modern technology. Of course, without a lot of the basics of technology it's really difficult to get the industrial revolution started. They need to try and convince other people to help them try to develop some technology, but they of course only know what is possible, not how to really do most of the things. For example, how many of us could build a water powered loom? Though that was one of the major starting points of the industrial revolution, and what would be considered most valuable in a medieval/early Renaissance society. Maybe it would be a good idea to make the hero someone with some actual skills. Like a plumber. That would be interesting. A plumber, trapped in another world, struggling with a society that only has outhouses and no running water, struggling to build a septic system that actually works with only the limited technology in the world he is in.
3: A character from the other world gets trapped in our world. Something like The Devil is a Part-timer, but less comedy, more drama.
4: Someone from our world is kidnapped and made a slave in the other world. He can't speak the language, doesn't understand what is happening, and just wants to get back home. This could allow for some interesting stories about power, freedom, coercion, etc.
Hell, even within the current crop of "isekai" stories there are totally different genres that have been developing in parallel with only mild cross-pollination. The "otome-game" style isekais are completely and entirely different from the stuff that has managed to penetrate into the mainstream western awareness, which absolutely take most of their trappings from a mix of shoujo-manga, bodice-ripper romance novels and, of course, otomege. It's a style highly distinct from both the "JRPG-isekai" and the old-school shoujo-manga isekai, with surprisingly little in common with either.
This is really interesting genre. Especially since most of them seem to reincarnate as the villian of the story. Usually the story then seems to be about how the story would have gone differently if the villain was a nicer person.
I mean, atleast with FoZ there's a certain fun to seeing how mad people get over the male protagonist having his balls busted. And honestly it seems to be that tsundere love interests were a moderating factor in the wish fulfillment of teen boy anime. They kept anime fuckboi protagonists in their place and without them all hell breaks loose
Actually, that's a very good point. Tsundere characters in shounen originally were mainly about pointing out the protagonist's lack of maturity. Basically his love interest is attracted to the good parts of his personality, but repelled by the negative parts. This is why she switches back and forth in her attitude towards him, and why usually as the story went on and the hero matured, she would stop being tsuntsun. (Manga Akane Tendo for example). Then the shoujo variation developed, where the tsundere was primary about
her immaturity, and how she needed to mature to have a good romance. Then that version seems to have migrated back into the shounen as simply one more character archetype to throw in to the mix because you gotta have a tsundere. Which is why a lot of modern tsundere fall flat, instead of agreeing with them that the protagonist needs to grow up, you sit there wondering why they are mad.
