For those cases where you're writing a native extension to primary bridge over to a native library, you may find either FFI or Fiddle handle your use case quite well.
But yeah, I agree with your point about native extensions. Ruby has gotten so much faster in every form in the past couple of years that I think we could bring a lot more "in house". I think there have been some efforts with this regarding Psych in core as well?
I'm curious whether this reflects MRI's improvements closing some of the gap or something else.
(Both running identical pure Ruby code, no extensions, in a long-running test scenario, no setup each time.)
To give one example, DB adapters work just fine.
Since I have you, if you could humor me at all, what do you think the biggest current sticking point to average Rubyists just flat out switching to TruffleRuby is nowadays? Or isn't there one?