This is just straight up false. You can compile subsets of the engine even in Godot 3. Godot 4 has made this a first class citizen.

C++ coding is just fine. It's not painful. It can be a bit of boilerplate to expose c++ member fields and functions to the rest of the engine but you get some great power out of that. Just use compile your own module right into the engine. Don't use gdnative.

As someone who's codes a lot of c++ in Godot I really am not sure what your talking about here.

SDL isn't even in the same dimension of usability compared to the Godot editor.