Thus, to a lot of people, an action anime aimed at younger audiences that's also girly is simply unacceptable to watch unless it's dark. Thus, there's a huge demand for edgy magical girl stuff and it's usually trash, abandoning the themes of the genre in order to appeal to weird adult men with gratuitous brutality, skimpy outfits on young teens, and subtle sexist undertones throughout the whole thing.
Demographics are largely a function, for TV, of airtime and for manga in what magazine the series appears. The times when young girls are watching TV differ on the whole from the timeslots where early to mid-20s male audiences are most likely to watch. This lets us know that most of the shows we're talking about here aren't aimed at a younger audience.
To this end, products are largely aimed at one or the other. Madoka, afaict was never competing for airtime with Pretty Cure. Mahou Shoujo Site, for example, appears in the same manga as
Baki a martial arts manga featuring fairly grotesque levels of violence.
These, quite demonstrably, aren't series aimed at the standard young girl magical girl demographics at all, but magical girl aesthetics creeping into the Baki audience.
Rather notably, this isn't really new. Cutie Honey is a very early and pretty iconic magical girl series, and one that was very much built on sex and violence (mostly sex), in ways that contrast heavily with, say, Sailor Moon to varying extents by incarnation.
Adopting a younger, less overtly sexual vs cute aesthetic, is fairly new, but this feels like it signals the exact opposite of what you suggest, a growing demand for 'cute' content among the mid 20s male audience that justifies taking pages from a
Baki or
Fist of the North Star or
Cutey Honey for more Magical Girl Site (or Madoka really, because let's not credit Site with anything) aesthetics.
By contrast, we've had genuine darker shows aimed at the shoujo demographic magical girl works usually target. Utena deals with some fairly serious issues and is firmly shoujo (though a bit older age range than Precure I'd assume). Princess Tutu originally aired on a kids network, despite being a go to darker show in the genre. However the darker content is largely subtext here, and the violence itself is heavily stylized. It's not an anime featuring torture or heads being ripped off.
Rather notably then, the 'problem' could be expressed as "people online talking more about the version of an aesthetic-based category that caters to them than one aimed at other people."
Pre-2011, I think we actually saw something more generally in line with what people complain about here. Namely, look at all the grimdark "Crystal Tokyo is a dystopia" type fanfiction and analysis in fan communities overthinking Sailor Moon. This is, often, taking the edgiest possible take on a work that, while it contains unhappy moments, is nowhere near Madoka or Site or Raising Project in terms of the duration or intensity of the bad things the audience is meant to feel. It's a fairly deliberate attempt to overread the happy ending and deliberately misconstrue what the author intends to create a darker, edgier world.
This is, if anything, more disruptive than people who really like Madoka a bit too much, because it intrinsically intrudes on a universe that isn't about these things and tries to co-opt it, and can easily co-opt ongoing discussions, insisting, not that Madoka exists, but that Sailor Moon always was Madoka and should be treated as such.
I"m a bit curious if emphasizing these darker takes in the past decade with a few prominent works has served to intensify the more iffy analyses out there, or to divert them now that there already exists prominent settings where this particular variation of the fantasy is enacted wholeheartedly and about as bluntly.
The fact people don't go back and witness the formulative years of the Magical Girl makes my soul hurt, there's so many gems and diamonds in the rough that are flat out some of the best fiction I've ever seen. Utena for an example is a masterpiece.
Utena is a late 90s anime. The genre's seeds are in a few works from the 60s by most accounts, so Utena, while a decidedly influential work, is hardly formulative years no matter how you slice it.