However, I don't think structured BINARY data is encountered as often on the interwebs as JUST structured data, and simpler textual formats like JSON, XML (and even csv) shine here, despite their shortcomings in terms of message size.

As for unstructured (or loosely structured) binary data like videos or large binaries (binary blobs is what I am talkin about), protobuf is as much as a poor choice as any other structured/schema based data protocols.

Protobuf has no tremendous benefit to any of the other binary formats like avro either, so I don't see why I should be excited about it. I wish google and the google ecosystem people stop trying to make it sound like THEIR simple schema based binary protocol is a big deal and try to shove it down our throats. For simple message passing around, I intend to keep choosing compressed JSON for the foreseeable future, regardless of what narrative some fan article is peddling.