Apart from the 51% attack mitigation, I think you are ignoring the fact that full nodes run by normal users are essentially what make bitcoin collapse/ takeover resistant. A system comprised only of miners (if there are no non-mining full nodes) or entities with the ability to run specialized hardware (for chains with large blocks and enormous throughput requirements) can never be as takeover resistant due to centralized points of failures.

A system with millions of user maintained full nodes will just trudge along, no matter what. That is a worthy feature to ensure robustness in the face of calamity (natural or man-made).