No issue with them being available for transfer from other games, although that's something I don't really care about so I wouldn't really mind whether that was available or not.
Up until this post, that's exactly what you were saying. Otherwise, why would you say from the get-go that you don't want every Pokemon in every game?
Gen 7 did exactly what you're now saying you want: the Pokemon available before postgame were ones that fit the regional vibe and culture or had storyline purposes, but the entire catalog was available to obtain through ways and means, whether that be through wormholes in the Ultra games or transfer from older gens. Everybody wins. Why wouldn't you just say that you want your games to be like this?
You made an example using pigeons and pandas, and how pigeons are boring because they're everywhere, while pandas are interesting and exotic because they're only found in one place. You also mentioned Unova, the most commonly hated gen dex (along with Johto) because of not only the uninspired copycat designs, but because the old mons were locked away until post game, so there was a lot of repetitiveness in encounters and battles. In other words, you were seeing those pandas everywhere. Can't have it both ways, unless you trust GameFreak to make 300+ completely original and varied designs every gen.
I keep seeing the same selfish reasoning from the "I don't want every Pokemon available" crowd: "The games should be tailored to my specific tastes."