I'm not referring to cart size. Bigger game = more work = less time to add Pokemon. That's what they'll say. If they were willing to not release any more games this gen they could add the rest via DLC, but sadly that's not how it works, and they have to start working on Gen 10 as soon as possible since Nintendo's next console is probably going to be 4k-ready.
How did they not have time to add them in SwSh when the wire frames for the Gen 1-7 models were identical to the ones in the 3DS games, aside from a small handful that had a few changes? This has been proven.
It's statistically impossible for one very complex wire frame to be created and be 100% identical to a previously created one. And yet this is the case for hundreds of models. Reusing these models was absolutely expected and was a great idea. And as much as I prefer sprites to 3D models, Game Freak was very smart to make all of those 3D models in order to futureproof the series. Why do people still act like the work wasn't done years ago?
Also, if time somehow WAS the issue, with as many Pokemon that are available on ALL of the Switch games by now--all using the same models--how is most, if not all, of the work not already done? Again, they are not remaking every previous Pokemon model from scratch for every new game. That would be stupid. So in Scarlet and Violet, what excuse is there when the work is done and additional content can be added?
And I brought up cart sizes because that was the issue with BDSP if you don't patch them right away. They were shipped on a cart that was too small for the full game, even though larger cart sizes are available, because that was cheaper. So you have to download a patch first in order for these games to not be a broken mess. Edit: Looking into this further, the smaller cart size to cut costs is fan speculation in a desperate attempt to understand why these games were shipped in an incomplete state. We still don't know.
So if that's the case, the file size
of the games can't be the excuse to not have every Pokemon, and not having enough time because a lot of work went into making a big game can't be the excuse when the models have been done for years.