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Even if I were to remove every Pokémon I dislike from Gen 5, the largest generation, there would still be 144 Pokémon from it that I like. By contrast, even if I combined Gen 6 and Gen 7, the two smallest generations, and kept all of the Pokémon from them that I dislike, they'd have 153 overall. If I did remove all of the Pokémon from them that I dislike they'd only have about 139.
The last two generations have proven to me that quality over quantity doesn't exist when it comes to Pokémon (or more accurately, when it comes to Game Freak), so having smaller dexes is strictly a negative if you ask me.