I tried to migrate to capn-proto but it just doesn't build on MinGW so I have no choice but to wait. Like you say, it gets worse the more I wait. But, if the APIs are somewhat sane, they should hopefully also be somewhat similar: Able to switch case on oneofs, movable data structures etc.

I don't like that protobuf has recently started linking with abseil, which despite being a good framework, I can't use it if it doesn't build absolutely everywhere I need it to. So, maybe I'll be forced over to CapnProto one of these days?