This problem is part of a bigger underlying issue that is only now starting to get attention thanks to the insanely bad decisions as of late. But I digress, I need to start at the beginning so bear with me here. This may come off rant-ish but I promise I don't mean it like that and will try to avoid that.
Game Freak as a developer have been hugely successful with the Pokémon franchise. I mean, they own the third largest gaming franchise in the world, and that at the hands of a small development team of just over 100. That success has been astounding, and has only grown with each generation. They realised that with their formula they can constantly chuck out games that fans will each up and reap the rewards. Over time, this has lead to them cutting corners and putting less effort into their games, as it hasn't been necessary for them to see success with their games. It's gotten to the point where fans will just buy the games now because "it's the new Pokémon game". Whereas other developers need to put work in to make their games the best they can be, with minimal effort GF can reap the rewards thanks to the reputation and scale of their franchise. Since Gen 6 onwards, game quality has declined drastically. Stories have become incredibly simple and hand-holding, puzzle solving is all-but irrelevant, and the designs have become lazy. Changes between XY and SM were minimal as far as design and story writing go. Post-game has basically disappeared now. The amount of new Pokémon released has declined over time, and only goes to demonstrate how the development team has become lazy. However, they're not just lazy because they are successful, there is a reason for the corner cutting and simplicity of newer games.
Game Freak has been chucking out new games at a faster and faster rate recently. What started with a 3/4 year gap between main-line games - 3 years between RB, GS and RS, and 4 years between RS and DP - has decreased to a one year gap since black and white. 2 years between BW and BW2, 1 year between that and XY, 1 year between SM and USUM and LGP/E and now SwSh. The trend is clear, they are pumping out a higher rate of games, giving them less time to work of the finer details. Why? Because their investors are only interested in one thing; money. How does that affect GF though you might ask. Well investors are the ones who hold the shares to the company and push the development with their investments. However this also grants them a say in how the company handles itself. If investors want x, the GF has incentive to grant x, lest the investors pull their support. Investors want to see the highest return rate possible on their investments, and obviously releasing more games at a faster rate does this. This means that in order for GF to keep up with the pressure, they have to cut corners in their games to keep to the release dates set by investors. This leads to very unoptimised, uninspired games like SM, USUM and now SwSh. This also leads them to take on more than one project at a time, such as working on both Pokémon Home and SwSh at the same time, as opposed to one at a time like before.
Bear in mind this is just theory, however it is highly supported by the trends of the data when you look at it. So when GF is told they need to make a switch game, they will take the easiest and fastest to implement solution possible. Reusing all old assets, getting the absolute basic essentials in place as quickly as possible to make a playable game recognisable as "Pokémon" that can be released to meet the investors' demands.
This lack of time leads to some very questionable decisions to ensure that the money keeps rolling in. They've spent so long on development of basic assets, that it's become infeasible to transfer all Pokémon assets to the new engine in time. That is, if you believe they will release the game without implementing every Pokémon and leaving only Galar Dex mons in the game. There is still the possibility that they will backtrack on this issue to lessen the blow of all the other short-comings of the game. But the main fact remains, those who are vocal about their dissatisfaction with the game as it stands are a vast minority. There are many many consumers out there oblivious to the development of the game, many children who don't look at or see the outrage, and will end up with the game since it is the "next Pokémon game" and many who will buy the game to feed their nostalgia towards their childhood spent playing RBY and so on.
The choice to remove all Pokémon not part of the Galar Pokédex was a bad one, but it was bad only for those who are now talking about it online. GF does not care about the minority, it cares about revenue, and as evidenced by the trends seen over the years, more frequent Pokémon games means more revenue. They don't need to put effort into the games because they will sell regardless. Will they back-track? Who can say. I doubt it based on their responses and it deeply saddens me to see a franchise I love deteriorate like this. But I've been dissatisfied with Pokémon games since XY, and this is just the cherry on the cake for me personally. There is no evidence to support that these games will be anything besides disappointing, especially when compared with everything that possible on the Switch if you look at games like Breath of the Wild, Mario Odyssey and so on. The potential for these games is lost due to poor time planning, inability to negotiate with investors and complacency.
Tl;dr Game Freak has become lazy due to pressure from investors and success of games with minimal effort. The decision to not include all Pokémon stems from that, and is unlikely to change which highly disappoints me, and I've resigned that this is where I will be taking my leave from the franchise. However this isn't a new issue with GF, only appearing in force now because of how visible the corner cutting and laziness is. But GF will not lose out because of this, since the majority of their audience will still buy the games, either due to not being aware of the issues with the game, or not caring and buying the game anyway.
There is a lot more I could say about the issue, both the removal of non-Galardex mons and besides, but I'll leave this post like this for now.
