The main reason for games not to be playable on Linux is the anticheat software used in modern online games. Pretty much everything else will now run perfectly (see protondb.com). Since the commentor you were replying to specified that they played old single player games they would probably be fine with just Linux. Indeed many sufficiently old Windows games are now easier to play on Linux than they are on modern Windows.
This is not as sure a deduction as it once was.
The main reason for games not to be playable on Linux is the anticheat software used in modern online games. Pretty much everything else will now run perfectly (see protondb.com). Since the commentor you were replying to specified that they played old single player games they would probably be fine with just Linux. Indeed many sufficiently old Windows games are now easier to play on Linux than they are on modern Windows.