It is difficult to tell sometimes due to its religious backward compatibility, but C++ has been becoming significantly less complex over time. I have a large C++ code base (originally hundreds of thousands LoC) that I aggressively modernize, essentially rewriting it idiomatically in new versions of C++. It was originally written in C++0x/C++11, rewritten in C++17, and is currently being rewritten in C++20. You can barely tell the code bases are related beyond being functionally similar.

It is also important to separate C++ the language from its standard library.

As C++ the language has modernized, it has dramatically reduced the lines of code to express a given thing. And the more modern way of expressing the thing has stronger type safety, more flexibility, and better composability. Things that used to require a lot of template metaprogramming magic to pull off are now clean one-liners. Particularly in C++20, which is probably the biggest step-change since C++11, metaprogramming is simultaneously much more powerful and much more readable. A lot of code that used to be written is now metaprogrammed. Previous use cases that required C macros largely have native C++ equivalents at this point.

The major issue that makes C++ seem complex is the standard library, which was largely designed and written for legacy versions of C++. If you use the standard library heavily, it tends to want to be used in the style of C++ for which it was originally written. If you built a standard library for C++20 from first principles, it would look quite different from the one we have. Hence the proliferation of non-standard "standard" libraries for C++.