Before microservices were a thing, I had the chance to work on a couple of telecom systems written in Erlang/OTP, but it wasn't until years later that I realized we were already doing most of the things people were using microservices for, with the single exception of being polyglot (although Elixir and Gleam are starting to challenge that).

Small teams were dealing with specific functionality, and they were largely autonomous as long as we agree upon the API, which was all done via Erlang's very elegant message passing system. Scalability was automatic, part of the runtime. We had system-wide visibility and anyone could test anything even on their own computers. We didn't have to practice defensive programming thanks to OTP, and any systemic failure was easier to detect and fix. Updates could be applied in hot, while the system was running, one of the nicest features of the BEAM, that microservices try to address.

All the complexity associated with microservices, or even Kubernetes and service meshes, are ultimately a way to achieve some sort of "polyglot BEAM". But I question if it's really worth it for all use cases. A lot of the "old" technology has kept evolving nicely, and I'd be perfectly fine using it to achieve the required business outcomes.