I think protobuf really works well on the backend and specifically with compiled languages like Go or C++ as per seen by the usage at Google and adoption of gRPC for Go based cloud tooling. Beyond that it's a huge failure. The generated code and usage for other languages is not idiomatic. In fact it's a hindrance and you can see that by the lack of adoption except by the largest orgs who are enforcing it using some sort of grpc-web bridge with types for the frontend. Ultimately you can just convert proto to OpenApi specs and do a much better job at custom client libs with that.

I'm not a frontend dev. Most of my time was spent on the backend but what I'll say is I much prefer the fluidity and dynamic nature of JavaScript and the built in ability to deal with JSON that naturally become objects. All the type stuff is easy to do but with docs you can get away with not needing it.

My feeling. Protobuf lives on for gRPC server side stuff but for everywhere else OpenApi is winning.