We aren't talking about the implementations, we're simply discussing the spec. Can you name another language spec that took over 15 years from conception to completion?
Even Common Lisp which languished for a terribly long time due to infighting didn't take that long despite being a much more comprehensive and difficult spec.
If you read carefully my original comment, you would have understood specs were part of the description.
Just as an example, C++ concepts were originally presented in 2005 [0], dropped in 2009 [1], redesigned as Concepts Lite in 2013 [2], graduated to technical specification in 2015 [3], added to C++20 roadmap in 2020 [4].
Making it 15 years to fully work out a language feature and related library functions, and even what came out 15 years is a subset of the original proposal, not going to bother with specification refinements after C++20.
Everything goes faster if it were us doing it, right?
Not everything evolves at the speed of TL;DR; attention span folks wish for.