I'm surprised that any of you are surprised by this. Let's Go only had 153 Pokemon, and you really think in the short time since those games that they've created HD models of all remaining 809 past-gen Pokemon and their various forms?
Let that number sink in EIGHT HUNDRED NINE
And let's be honest, even if all Pokemon are currently programmed in, they still wouldn't let you transfer as easy as Pokemon Stadium did. They've neutered the feature before and they'll do it again. Yes it sucks, but just wait till the third versions/sequels/gen IV remakes for them to relax the restrictions and turn normal transferring into a selling point.