Has it really been that long? Apparently so. Valve originally announced their rebranding of Steam Play with Proton back on August 21st, 2018. Seems like a good time for a quick reflection being halfway to a decade old now with the tech that gave rise to the Steam Deck.
The only (large enough) area which is currently lacking is multiplayer games, especially those with anticheats. Unfortunately, there’s nothing users can do about that other than wait for game developers to enable wine support, which, despite EAC and Battleye significantly simplifying the process, many still haven’t done.