I would also add on that as the number of pokemon climbed higher and higher, you started to have a lot more "redundant" pokemon.
Like, how many pokemon are just birds? It was fine for Pidgey; but, Starly and Pidove just feel like "Pidgey, but slightly different" from a looks and a gameplay perspective. This also happens with Spearow and Ratata - there are slight variations that take on a similar role in the game play (most of those being ones to just collect/fight in random battles).
The game just isn't deep enough to justify literal copies of pokemon (there is a ~10 stat difference between Pidgey, Starly, and Pidove's final forms and all of them are normal/flying - for example and none of them would be considered competitively powerful) and as more pokemon come out, the more copies or slight variations that exist and the more boring the whole thing becomes.
The starters also suffer from this, with them most commonly being a 3-stage water/fire/grass type with some slight variations (usually dual-typing) as do the legendaries (which are frequently /psychic, /flying, /dragon).
Cool pokemon are cool, but it gets a bit tiring when so many are kind of boring.