There’s no reason btrfs shouldn’t work for every use case.
That said I think the slight performance gains of ext4 over btrfs make it worth sticking to ext4 for games. Imo it’s similar to as if you had you main system on an HDD but ran games off of an SSD; that’s how much faster it feels.
I would install games to a separate ext4 partition but steam to btrfs (for configs) in that case.