C++ has plenty of issues, but it's really not that bad, especially modern C++. It's a huge language with tons of features, many of which you'll never use, but as far as writing C++, really not that bad. I've written a lot of C++ over the years, and I've also written a lot of vanilla C. I can tell you that you can definitely get a new project up and running much faster in C++ than in C.
If you are not using classes, you are not using OO at all, by definition.
That does necessarily not mean you are programming badly, although you might be. But restricting yourself to STL and smart pointers does very strongly resemble Java Disease. You might as well switch to Java.
I write Rust too. I like Rust for the mostpart, though there's some issues with the language that really wind me up, mostly to do with the unsafe/safe code boundary.
If you want full control and easier interfacing with the OS, C++ is probably a little better, but Rust is definitely a little easier to work with once you learn the language.