The 20th anniversary actually gave a reason to GF to take advantage of the Pokemon as a franchise and sell more.
Who actually would buy the first gen pokemon aside from the nostalgic players, or retro players? I'm a casual (but old) pokemon fan and even if GS came to the eshop (my fav gen) I would still not buy them.
Plus, now they have a reason to launch a "new" product that will try to sell nostalgia. We've seen this strategy so many times, and Pokemon can't but use it as well, now that the sales are getting lower with each gen. So, only smart marketing would save the series. But WHO's the target audience? Old fans of course. Pokken is a homage to old school fans, with even the developers admitting it. It makes sense to try and win those guys back.
I don't want to make things look tragic, like GF cares about money and stuff. H*ll no. I just say that as of now Pokemon was interested in making games. Now it's interested in surviving. The classic formula isn't enough anymore. So, GF had to turn into a new direction.
That said, I agree with the marketing and I'm ready to help, as long as the games/products are worth it and not lazy work. So, as long as GF provides quality fans we'll be there.
Last but not least, Charizard for Pokken isn't fan service. Mewtwo is, for its two forms. I could know nothing about Pokemon, but I would still pick a dragon on a fighting game, but not an anthropomorphic Frieza. And for crying out loud, why waste a slot for Pikachu Libre? To me that makes 0 sense.