Catalina will end support for all 32-bit apps, including games.
MacOS Catalina

When Apple rolls out their upcoming Catalina update for their MacOS, it will kill off the ability to run any 32-bit apps, including all 32-bit based games. This update was originally slated to hit Fall 2019 but was pushed back to the upcoming update to the operating system.

Apple first announced this move to end 32-bit support back in early 2018. So while this shouldn't be too surprising for some people, it is still a cause for alarm for those who are using apps that were not updated for one reason or another. It could be that some apps and games were never updated because the developers no longer exist, or it wasn't financially feasible to update, or it was technically impossible to update.

For example, most of the games made on Unity prior to 2016 (version 5.5) will no longer run when Catalina drops. Unity, prior to version 5.5, had no support for creating 64-bit apps for MacOS. This could potentially have a big impact on a number of Indie titles that were released over the years. A number of the studios that released these titles may not have the means to update their old titles to a new engine that supports 64-bit and get a new release out the door.

This move by Apple follows what they did for iOS apps. When iOS 11 launched in November 2018, it also ended support for all 32-bit apps. Just like now, not every app and game was able to be updated, thus killing those apps that were once usable.

The silver lining here is that Apple stopped accepting 32-bit app submissions for MacOS near the beginning of 2018. That means that if a game or program came out any time over the past year and a half, they should continue to keep working once you update MacOS to Catalina.

Catalina is slated to arrive later this month.