>>55537600this is for more than just "old good, new bad" though. Gen 5 had it's new pokemon take up the spotlight more than ever, but starting in Gen 6 the new mons always shared the spotlight with some new thing for old mons (megas, regionals, gigantamax, paradox/convergents). Plus we haven't had a NEW roster of Pokemon totalling over 100 since Unova.
Pair that with Gen 6 onwards dex sizes being a lot bigger (Kalos had 457, compare that to Hoenn's 202 or even Unova's 300.) New Pokemon still get attention, but apart from starters and legendaries they certainly don't get it like they used to.
And then it's also probably at least partially just because the newer mons haven't been around for as long, so people aren't really as connected with them.