That's great for you, but unfortunately doesn't match my experience. Large, old codebases tend to become a mix of all "eras" of C++. That's either because old code was never completely reworked, or because newer programmers pick stuff up in the wrong place, for example from an old blog post.

The problem then is that some of the advantages of modern C++ are a bit "all or nothing". Just to pick an example, for exception safety in the current sense to really work, basically all of your code has to be written in a certain style, which is something that's really hard to achieve.

Maybe that's less of a problem for codebases started after 2011 that have been written in the modern style from the beginning. But given the way the C++ language continues to evolve, my bet is that even those will eventually run into the same problem with whatever new feature is introduced in 2026. There really needs to be a way to deprecate old language features.