Utter nonsense. Literally none of that is true, we know magic has done nothing but improve. The invention of apparition, the memory charm, continual improvements to potions, and so on. Famous people discovering things that made them famous in the past doesn't mean equivalent progress is not happening now. Dumbledore is a "modern wizard", and was perfectly capable of working with Flamel to discover new things.
The Department of Mysteries regularly studies magical phenomenon, going so far as to undertake organized study of things like Time, Death, Thought, and Love.
It is advancing, but not at the same rate. Hogwarts, for example, is still a marvel of the magical world. It is one of a kind, and feats of such magic has not yet been recreated.
Apparition has been around for who knows how long, there is no indication of when it was made. Same with the memory charm.
Using the example of the sword is laughable at best. Hell, at no point did Harry penetrate the Basilisk's hide with the sword anyways - he stabbed it through the roof of its mouth up into its skull, and that's all. What did that sword accomplish that casting that the roof of its mouth couldn't? Not to mention, do you honestly think a sufficiently skilled wizard or a sufficiently powerful spell wouldn't get past that level of defense anyways? Being able to block a few charms isn't the same as blocking potent curses.
It went up to, and THROUGH the skull, along with the scales on the other side. Again, said scales capable of blocking the cutting curse.
You can't use "sufficently skilled" as a qualifier. A sufficiently skilled wizard could blink a Basilisk out of existence, lift Hogwarts off it's foundations, and turn it into a giant swan.
The fact that such a famous wizard had a famous novelty item that was a standard fashion accessory during the time he lived isn't proof of much at all. Here, you want an example of what I'm talking about? Sirius' pocketknife. Sure, you can use it to open locked doors. Potent ability. But do you honestly think Dumbledore couldn't open any door that thing could and then some? Why waste time making the pocketknife then, if you could instead use that time to be Dumbledore?
It was not a novelty item. It was a item of such worth, that the Goblin King himself wanted it (it's made of silver and ruby, but so what, goblins have plenty of those, it wouldn't be worth as much effort as he put into trying to get it, the value had to be the magic enchanted in it).
And while Dumbledore could cast charms to open almost any lock, do you not think that if he took the time, hours, days, maybe even weeks, to create the best unlocking device he could, said device isn't better than something he can cast at a moments notice?
Brewing potions takes time that could be used for other tasks. It also takes ingredients, which take time to gather or purchase. Time is one of our most valuable resources, and I'd rather not waste it like that. Having a few potions in case we lose our glasses is fine, but not having to brew a large amount of them.
Let's spend a hour, and make a bath-tub's amount. Unless we drink the potion by the gallon, that should last us ATLEAST a year.
Besides, I'm fairly certain that if the Oculus Potion could cure near-sightedness nobody in the wizarding world would wear glasses. Seeing as many characters do wear glasses, that's clearly a problem they haven't solved.
Maybe not cure, but probably treat. Stand-in for glasses. As for why people don't, for one is money, not everyone is rich with a infinite well of money like us, two is most people don't know how, while we can brew it with our eyes shut (metaphorically).
