I think you're just getting older, to be honest. I had a lot of issues digesting the newer gens too, for similar reasons. But you know, they're not all that bad. Just relax and accept it. The vast majority of gen1 pokies were excruciatingly cute and often stupid too (psyduck as the most notable example). All gens have cute ones (Pikachu - Sentret - Plusle etc), weird ones (Staryu and Magnemite - Dunsparce - Bronzor etc) and epic looking legendary/dragon ones (Dragonite, all the way up to Hydreigon - Mewtwo, Raikou, Rayquaza, etc.). But gen1 will probably have a special place in your heart because of the magic of it when you were a kid, and the newer ones lack that for you. And that's normal, but that doesn't make the newer gens worse.
The anime work more closely together with the games now and that's been really noticable. That was entirely different in gen1 and to a lesser extent gen2 also, which is easily notable by how the sprites differ from the anime ones (Ghastly f/ex). I think that has definitely influenced the newer pokies' looks. Plus, the show is aimed mostly at younger kids, which you were once, during gen 1, too - so please consider that before bashing newer gens. You're getting older.