Cap'n Proto

Looks like this has been around for over a decade now. I'm surprised I haven't heard of it until now.

If, as advertised, it's significantly better than protobufs, why hasn't it gathered more steam/adoption? If presented correctly it sounds like a great alternative/replacement to things like JSON, proto, SBE messages, ... Especially in the realm of backwards/forwards compatibility.

Has anyone tried this out and ended up switching BACK to a more widely used alternative? If so, why?

Also note cap'n web, which is half a year old more web friendly version, https://news.ycombinator.com/item?id=45332883 https://blog.cloudflare.com/capnweb-javascript-rpc-library/