A number of things can be integrated into games from steam (Documentation here: https://partner.steamgames.com/); the question is what would you like to see, or examples of other game with steam integration?
A list of some of the basic things that steam can do (just listing a good number even if it makes no sense):
-Achievements
-Stats
-Matchmaking
-Multiplayer
-Steam leader boards
-workshop
-In-game transactions
-steam friends
-remote play
-anti-cheat and security
-events and announcements
-Steam points shop
-Community items
-Steam deck compatibility
-Analytics and reporting tools
I know Achievements are already in the talks in a number of community's; I wanted to give my input that Achievements like "played world 15" is not a good achievement mainly because it becomes impossible to earn it in the future and locks out completeness type players.