You can debate the design decisions all you want (and I agree `std::string` was a poor choice here)... but it's kind of absurd to say that a technology underpinning products used by billions of people every day is not "serious".
Would you go through all of the effort to rig an application with userspace networking only to return its results inside an `std::string` -- one of the few std containers where one can't even control the allocator if they wanted to? That's absurd, if anything.
Google does all of that when it makes sense, and yet uses it to push protobufs. That’s the entire point: you are calling it absurd and non-serious, but this only shifts my opinion on you, not on Google.
But you seem to be arguing that Protobuf is bad because it is not well suited to certain use cases, dismissing all other use cases as "non-serious". That is offensive.
In fact, I can just do that now: Protobufs is bad. You seem to agree, because you haven't even advocated for it -- just flatbuffers and Cap'n Proto and the phonebook of alternatives. Listen, I don't care who you've worked for or what you've done. As a scientist and engineer I'm totally ready and able to entertain critiques of my prior works without being offended. I'm offended that this is the quality of your participation here.