I just write standard C++ or C code and it compiles fine. Hard to complain about that too much if I don't care to use the extra features. You can just access registers directly even if you use the Arduino IDE and configure things yourself if you want.

But yeah, I'd personally use visual studio code if I wasn't going to want to use the arduino libraries anyway. It's not a great editor. VS Code probably isn't that great either, but it's good enough for the little coding I do (I mostly design circuit boards that frequently use these little boards as brains).