They have so many die hard fans and lovers of their IP that they get away with a lot. There hasnt been a pokemon game that was actually exciting to most fans in over 15 years but people that grew up playing red and blue and watching the TV show will still buy every game.
To be fair, what would people expect from Pokemon besides redefining the core mechanics? The physical/special split was 13 years ago, arguably the biggest and best change in Pokemon. There are only so many ways one can improve a turn-based RPG without it becoming too complex for kids to enjoy (graphical improvements not withstanding).
It feels like they designed themselves into a corner here.
The problem with Pokémon isn't a dearth of new ideas (the fairy type is a great addition, as well as EXP share and several newer improvements).
The problem is there are more and better animations in Pokémon coliseum (an N64 game) than the latest release. When every move amounts to
- Move Pokémon towards opponent
- A few sparkles
there's just no reason to care about any individual Pokémon (or even type) anymore.
