Avro (and others) has its own set of problems as well.

For messaging, JSON, used in the same way and with the same versioning practices as we have established for evolving schemas in REST APIs, has never failed me.

It seems to me that all these rigid type systems for remote procedure calls introduce more problems that they really solve and bring unnecessary complexity.

Sure, there are tradeoffs with flexible JSONs - but simplicity of it beats the potential advantages we get from systems like Avro or ProtoBuf.