The success of XY is to blame for the shittiness of the following games. When they were being developed we were told that Gen 6 would be a bit barebones due to bringing every single pokemon into 3D. I think it can be forgiven for that reason. What can not be forgiven is that it was so successful, GF decided to put in that same barebones effort into every following game, despite the time and resources available now that futureproofing models was out of the way. There is literally no excuse for SM and USUM to be as shit as they are.