There was still Wine, and PlayOnLinux helped further, but when I looked for a game I wanted to play on WineDB, there was no guarantee it even had an entry, and if it wasn’t listed as “platinum”, the chance of you experiencing any reported issue was very high.
Not to mention, playing Steam games that weren’t native was an impossibility.
Thankfully I was more of a console gamer at the time, and I got a lot of enjoyment out of the few games that received Linux ports - like Team Fortress 2!