I don't think it's quite as bad as that. Especially in systems that are tied to monetary value, where irrational actors are punished monetarily, you can assume that the irrational actors vanish from the system over time. Those models often come with a specific bound on how many actors need to act rational (usually 33, 50 or 66%) for it to hold up.

I'm curious though how many actors act rational in specific economic systems. Especially with cryptocurrencies I feel like the low amount of rationality might be a significant hurdle to establishing a robust economy, even if everything else is ironed out (proper use case and incentive system).