After gen 3 GF slowed with changing or adding important battle mechanics and after gen 4 they haven't really done much at all.
Gen2:
>introduced held items
>introduced two new types
>made the special stat into special attack and special defense
Gen 3
>introduced double battles
>introduced abilities
>introduced natures
>changed the way EVs worked
Gen 4
>introduced the physical/special split
Gen 5
>introduced triple and rotation battles which are mostly irrelevant
>introduced hidden abilities which are a fraction of the importance of the addition of abilities themselves
>Gen 6:
>introduced the fairy type and tinkered with the steel type
>introduced megas which are specific to a few Pokemon
Gen 7 and 8
>have their own temporary gimmicks that, in the case of the former, has been replaced and designated to the dustbin of history, and in the case of the latter the same will happen next gen
Why have so relatively little revisions happened when it comes to battling after gen 3/4? Is GF lazy or is there just not much of a need to bring more to the table? What revision(s) or additions do you think should be made?