I think you described not monolith vs microservices, but single person working on a project and making decisions vs multiple. “Everyone’s responsibility is no-one’s responsibility” works the same way if multiple people work on the same microservice.

Also a monolith may (actually, must) have internal public interfaces through which components must communicate, and those contracts are more enforceable, amenable to static checks, and much higher performance that microservices’ network interfaces.

monoliths can be anything under the boundaries. That's why people get this so wrong. There is no rule that says you must have internal public interfaces (misnomer? how can it be public, but internal, at the same time?). Microservices were entirely designed to split work across teams.