I'm definitely in the "Pixar has fallen off" crowd. I have young kids so I see these movies a bunch. I'm not saying the newer movies are shit, or unwatchable, but they're just "fine", whereas several of the older movies are truly magical.
Last truly great one IMO was Inside Out in 2015. Coco, TS4, and Soul were all very good. Everything else since then has been just OK. My kids liked them, they're well made, it's a pleasant enough way to spend 90 minutes, but ultimately forgettable. Haven't seen Lightyear or Elemental yet.
Compare that to early Pixar: TS1, 2, and 3, Nemo, Incredibles, Ratatouille, and WALL-E. Holy shit what a run. Even Cars and Monsters, Inc. have a freshness to them that the newer stuff doesn't IMO. In a way, they're victims of their own success because they trained us to expect something fucking amazing pretty much every time for the first 15ish years.
Maybe it's just nostalgia as people my age have gone from the target audience for Pixar movies to parents now. I don't think so, though. We actually just rewatched Nemo the other day, and as a grown man - that is just an incredibly well made movie. Something like Luca or Turning Red just isn't even in the same ballpark.