Yeah all the New Super Mario Bros stuff was pretty weak. all of them had more or less the same art-style (generic mario stuff) and play-style (stripped down controls that got monotonous quickly) and they cranked out so many of them that after the first one they stopped seeming like new Mario games and just started seeming like DLC of new level packs for the same game. Mario 3d world was almost worse, because they brought it back to 3d but then did nothing with it because the levels were just as blandly linear as the 2d ones. You can only really identify these games by the power-ups that only show up in the games (the one where you can be a cat, the one where you're a bee, the one where you're a squirrel, ect).
Then Mario Maker came out and rendered all of those games redundant since there was an endless supply of genuinely creative levels in that 2d style now available. (if you were willing to go out of your way to find them at least). I genuinely don't think Nintendo should ever do another 2d mario game. There is nothing left to squeeze out of that style. The original main 4 Mario games were the peak of that style, there is no improving on them. Mario World came out in 1990 and Nintendo has never been able to top it with a game in the same style. Yet they kept trying.
Mario 64 on the other hand was fantastic, but there were clear improvements that could be made with it but only some of which were implemented into Sunshine and Galaxy (Galaxy upon reflection doesn't hold up that well. Again, it gets held back by how linear it is and how "generic mario" it feels, though it's nowhere close to being as bad as 3d world). Odyssey feels like it develops all of 64's best qualities and then adds tons of new stuff that all works and keeps things fresh.
It's curious how Odyssey actually gets rid of, or drastically changes, so many of Mario's core mechanics. Odyssey has no lives system, no meaningless points, no coins that don't have a point to collecting, mostly brand new enemies, an entirely new sidekick character, and no power-up mushrooms of any kind! Yet it ends up so much better because of all that stuff, and ultimately it feels like a celebration of mario as a franchise.