That's about right in my case. 2019 was more or less the years we switched to C++11. Some projects started using C++11 way earlier, and we still have some code

That's about right in my case. 2019 was more or less the years we switched to C++11. Some projects started using C++11 way earlier, and we still have some code we keep C++98, so, 8 years. Anyways, I don't know what you are calling "modern" C++, but for me it is C++11 and up. C++11 to C++20 introduced a few major changes but none as pervasive as C++98 to C++11.