Honestly, the truth is Japan is to blame. All their designs have been leaning towards this trend for a while now. Even designs that were already like it have had to emphasize it more (see Shin Chan over the years)
Game Freak just has to keep up with what's popular in Japan.
I saw a video where Japanese people were reacting to the Detective Pikachu trailer for the first time, and all of them (even the young adult men on the street) commented how it was weird to see the Pokémon look realistic and scary when they usually are supposed to look cute.
Japan's perception of Pokémon takes priority to them.