gen 5 started gym leaders having only 3 pokemon at most
gen 5 started the elite four having only 4 pokemon
gen 5 started rivals handing you constant free healing items
gen 5 started free lucky egg
gen 5 started putting a chansey expy in every route
gen 5 started doctors in every dungeon area
gen 5 started making the region a straight path to prevent people from not knowing how to progress
gen 5 started npcs explaining mechanics to you even when you tell them not to explain mechanics to you
gen 5 started westerners making ugly pokemon
gen 5 started poison not damaging you in the overworld anymore
gen 5 started the removal of content we'd never see in any future game like safari zone, game corner, battle frontier, and more
gen 5 started giving you a gift pokemon specifically to deal with a type disadvantage against the gym leader
gen 5 started making strength boulders 2x2 tiles to make puzzles with them non-existent
gen 5 started diversity
gen 5 started making the region a foreign theme park gimmick region