> You must be young. XML and XML Schemas existed before JSON or Protobuf, and people ditched them for a good reason and JSON took over.

I'm not sure you got the point. It's irrelevant how old JSON or XML (a non sequitur) are. The point is that one of the main features and selling points of protobuf is strong typing and model validation implemented at the parsing level. JSON does not support any of these, and you need to onboard more than one ad-hoc tool to have a shot at feature parity, which goes against the blogger's opinionated position on the topic.