I was following their Dota project from the beginning, and I think what they did made sense. Their goal there was to demonstrate real time decision making and teamwork in a complex environment without perfect information. OpenAI Five did a splendid job of doing that.

I would view it as the equivalent of making self-driving cars that are constrained to a single city. Sure, it doesn't have the full capability that a human would have. But who cares.