I think what annoys me most is when a standard is implemented except for an important feature. E.g. ranges was unusable for ages on Clang. And modules is still not quite there. I want to use the latest standard to get these cool features so I can write code like it's 2025, not 1980. If the biggest features are unimplemented then why upgrade? My concern is the trend continues, and we get cool things like reflection, but it takes 10 years to be implemented properly.
Wow, the list of papers for Modules is large. I can understand why it is taking so long to implement. Also, there needs to be "fingers to do the typing". I assume most of the commercial devs (Google, Apple) just don't think modules are important enough. It looks like Concepts also took a very long time to be fully implemented. Hell, that feature was discussed for 10 years (a dream of Bjarne) before approved into a standard... then maybe 5 years to impl!
When I was in college in the 90s, templates were new and had iffy support. In the 2000s, STL was still problematic. I remember the Microsoft Compiler spitting out error messages on STL types that were so long the compiler couldn’t handle the string length and truncated the error message so you couldn’t see what the problem was. In the late 00s and early 10s I worked in games, we wanted stability and for the code to be as non-tricky as possible (for example by banning use of exceptions, STL containers, and most casual heap allocation, among other things.) So we used older compilers by choice. My current job publishes an SDK and APIs that people have been using for many years, they need to be backward compatible and we can’t impose recent language features on our users because not everyone uses them, we have to stick to features that compile everywhere, so I still see lots of C++{11,14,17}.