The problem of middleware, other than needing a library per language, is that it moves the concern into the app rather than the host. I see a service mesh more

The problem of middleware, other than needing a library per language, is that it moves the concern into the app rather than the host. I see a service mesh more as extending the network functionality of the host OS and cluster than the app, which arguably makes rolling it out across a large disparate organisation more feasible.