Pokémon with all Pokémon available would be identical games. As in
>No actual National Pokédex in the Gen III-VI sense, would be like Gen VII where the Pokémon technically exist internally and can be used if traded into the game. There is nothing tracking how many Pokémon you catch beyond the regional Pokédex.
>Missing Pokémon likely have little to no presence in the games themselves
Articuno, Zapdos, and Moltres in Gen II have more meaning and presence in those games than Shuckle, Carnivine, and Cryogonal in Gen VII in its entirety. And that is to say that Articuno, Zapdos, and Moltres may as well not have even been in the games because you can't even encounter them. It's just a trade forward from Gen I. They don't improve Gen II by merely existing in the code. But at the very least they have value in the sense that they're used to complete the Pokédex in Gen II (also that they have new sprites).
Sword and Shield would still be just as much of a dumpster fire if it has those Pokémon internally. You are not getting new encounters or interaction with its world. You are not finding new secrets or discovering anything new. It's like comparing Unown in GSC/HGSS, FRLG, and DPPt to RSE. The latter is a nothing experience that's equivalent to any trade, and I would not count them as an asset to RSE much in the same way I would not count the God Stone in Gen V as an asset.
