For GUI, I've been very happy with grpcui-web[0]. It really highlights the strengths of GRPC: you get a full list of available operations (either from the server directly if it exposes metadata, or by pointing to the .proto file if not), since everything is strongly typed you get client-side field validation and custom controls e.g. a date picker for timestamp types or drop-down for enums. The experience is a lot better than copy & pasting from docs for trying out JSON-HTTP APIs.
In general though I agree devex for gRPC is poor. I primarily work with the Python and Go APIs and they can be very frustrating. Basic operations like "turn pbtypes.Timestamp into a Python datetime or Go time.Time" are poorly documented and not obvious. proto3 removing `optional` was a flub and then adding it back was an even bigger flub; I have a bunch of protos which rely on the `google.protobuf.Int64Value` wrapper types which can never be changed (without a massive migration which I'm not doing). And even figuring out how to build the stuff consistently is a challenge! I had to build out a centralized protobuf build server that could use consistent versions of protoc plus the appropriate proto-gen plugins. I think buf.build basically does this now but they didn't exist then.
No need to be snarky; that API did not exist when I started using protobuf. The method was called `TimestampProto` which is not intuitive, especially given the poor documentation available. And it required error handling which is unergonomic. Given that they switched it to timestamppb.New, they must've agreed with me. https://github.com/golang/protobuf/blame/master/ptypes/times... <-- and you can still see the full code from this era on master because of the migration from `github.com/golang/protobuf` to `google.golang.org/protobuf`, which was a whole other exercise in terrible DX.
In general though I agree devex for gRPC is poor. I primarily work with the Python and Go APIs and they can be very frustrating. Basic operations like "turn pbtypes.Timestamp into a Python datetime or Go time.Time" are poorly documented and not obvious. proto3 removing `optional` was a flub and then adding it back was an even bigger flub; I have a bunch of protos which rely on the `google.protobuf.Int64Value` wrapper types which can never be changed (without a massive migration which I'm not doing). And even figuring out how to build the stuff consistently is a challenge! I had to build out a centralized protobuf build server that could use consistent versions of protoc plus the appropriate proto-gen plugins. I think buf.build basically does this now but they didn't exist then.
[0] https://github.com/fullstorydev/grpcui