CrazyDuck

I'd say it depends entirely on your mindset. I've been enjoying playing it casually. There's both a ranked and unranked mode, but even in the ranked mode on lower ranks it's pretty fun to just mess about. It does require you not to focus on chasing rank

CS:GO is free to play and about to get a big update/overhaul into CS2. It's a valve game so it's bound to work great on steam deck