>>57974784>gen2 split special stat and added field conditions (weather, hazards, screens, etc), dark/steel types, and held items while reworking OHKO moves, critical hits, and a lot of other things>gen3 added double battles and abilities>gen4 added the physical/special split and trick room>gen5 added... triple/rotation battles which are, outside of maybe 3 or so exceptions, only used in battle facilities and very niche competitive formats. also team preview exists now if you count that as a major mechanical change>gen6 added fairy type, mega evolution, terrains, and nerfed weather abilities to no longer be permanent>gen7 added z-moves and removed triples/rotation battles (kind of a shame but they were wasted potential anyways)>gen8 removed megas/z-moves and added dynamax that'd be gone the next gen>gen9 added terastalization which is gonna be gone the next gen, and changed hail to no longer chip non-ice typesyou just made me realize how little the battle system has changed since gen 4 when counting removed features
there's a single new type, terrain moves/abilities, and no more permanent weather
and that's it
all that's really changed beyond that are the mons and the moves they have access to, but as for the system itself, it's barely changed