After reviewing and experimenting with service mesh offerings, isn't Service Mesh a monolithic (ironic) solution for a microservice universe?
Actually, I think they are a logical side effect of a microservice universe. One of the largest drivers for moving to microservice architectures is to separate concerns such that individual services implement very specific functionality very well.
For example, a translation service should take input text in one language and convert it to output text in another language. The team writing that service should consist of generalized developers and specialized linguists. Yet, in many cases we force the developers of this business logic to concern themselves with other things (e.g., transport layer security, access control, metrics collection, announcement and discovery).
The point of a service mesh it to treat the networking of microservices as almost another microservice. It's a specialized concern that, when treated that way, allows others to focus on doing what generates revenue or solves problems.
There is a reason much of the push on microservices is coming out of companies and organizations who are pretty deep in the microservice universe at very high scale. It should also be noted that most service mesh control planes are implemented via microservices, not monoliths.