redundancy, rolling updates or byzantine fault tolerance in a monolith > naïve assumptions that one part of your system going down won't mess up it's overall usability by and large just because you've used microservices
Micro services alone aren't enough. You have to have proper observability and automation to be able to gracefully handle the loss of some functionality. Microservice architecture isn't a silver bullet, but one piece of the puzzle to reliable highly available applications that can handle faults well