> And with STL, it still took another 5 years for the compilers to be good enough.

This is under-stated, IMO. It wasn't really until 2004 or even later that we had high-quality support for C++98 in GCC. LLVM wasn't available, yet. Heaven help you if you wanted to develop in C++ on OSX, since Apple's packaging of GCC was a total disaster. Step zero for developing C++ on OSX was "install GCC from FSF sources" for many years.

Even MSVC support was lagging. It wasn't until the Microsoft tools leadership got involved with C++11 that MSVC took standard support seriously. They were already prioritizing .NET in that timeframe.

Meanwhile, the big open-source desktop C++ libraries (Qt and WxWindows) still don't fully take advantage of the types and features in the standard library in 2021.