I don’t think binary serialisation counts as a good thing to include in the standard library. Unless Golang found a way to do it securely unlike other languages, which typically see binary serialisation as one of their larger mistakes.
Lack of interop with other languages is still a bad idea (the lesson of Java RMI), and I thought Google agreed. Having all the C++ and Java and Python services speaking Stubby was one of the most futuristic experiences there.
And as for .NET, Python I never saw any reference about such regrets, while ISO C++ is still discussing papers for some kind of future support via static reflection.
Here’s a discussion for .NET core not adding support for security reasons (eventually overruled for backwards compatibility reasons unfortunately). https://github.com/dotnet/corefx/issues/6564#issuecomment-21...
Java: https://www.bleepingcomputer.com/news/security/oracle-plans-...
Also the official path forward for WCF is gRPC, which also supports binary serialization.
As per Java, Brian Goetz has spoken multiple times about it, but the issue was mainly due to how the whole thing is designed, not necessarily due to using binary formats.