The header-only libraries are good. Less dependency is good. No need for build system is good. Many of the existing solutions you mentioned have tons of dependencies. When code needs to be built reliably on 3 different OS and interfaced with arcane twisted build systems, dependencies become nightmare. Boost is great overall but I rather avoid this monster if I can.

Yes, especially if data has to be consumed by different languages. Personally, I don't see a need for yet another C++-only serialization framework.

Here in 2018, we still have to roll our own.

Libnop has the right idea, but still fails on two important points:

a) Versioning is a must-have feature. (And no, some weird non-standard 'table' type is not a replacement.)

b) The wire protocol needs to be human-readable ASCII. (Or at least a human-readable ASCII with no performance degradation option must be available.)

Take a look at the binary format spec:

https://github.com/google/libnop/blob/master/docs/format.md

The format is designed specifically to provide enough structural information that the binary format can be parsed without knowing the original structure definitions. This makes it easy to write a binary-to-string converter than can grok any payload with minimal complexity. Message observability was a primary goal during development.

Writing a binary-to-string converter sucks. You write code once, and debug it every day. Anything that makes debugging harder is humongous pain that shouldn't exist; binary-to-string converters can be written, but let's be real for a moment: this is something that is dead last on the list of business priorities. If your message can be parsed with ad-hoc shell or Python scripts, that's a huge win for everyone.