Perfectly balanced games are plentiful, take rock, paper, scissors as an example.

What makes those games interesting is the concept of Yomi[1] and learning to read an opponent. There's a decent amount of literature in the fighting game space and a bunch of other genres overlap as well.

I remain pretty skeptical of ML being a primary tool here since a lot of Yomi is psychological and not necessarily an optimization problem.

[1] https://www.gamasutra.com/blogs/CalebCompton/20190211/336365...