An appeal to nostalgia is a claim that more or less boils down to "things were better in the past."

The NES era has a special place in my heart because those were basically the first games I played and those stick with you. But... I am not about to claim that modern equivalents aren't as good. And I don't feel the need to prove otherwise because I know that it isn't their objective quality or lack thereof that made them special to me. So the question is why is it so important to you that you can "prove" the PS2 era 3d platformers were objectively superior? Are you going to suddenly flip a switch in your head that changes your opinion of them if someone manages to "prove" otherwise?

AND you have to keep in mind that you are more likely to remember good games and forget mediocre ones. There is a bias toward older games being thought of as being better because most of the garbage ended up being lost to time. Today's stinkers are still fresh on everyones' mind.

noooo its just nostalgia!! games weren't better, they are better nowww!!!

Games in general have gotten worse, the quality only exists in the indie space nowadays. But there's 1000s of them, so it's not easy to find the gems. As for 3PP platformers... I guess the genre isn't all that appealing to developers. Maybe there will be a new one when someone has an idea for a new fresh take on it. Great games are made from great ideas and passion, rather than them being made to fill a gap in the market.