For what it's worth, one could probably make a basic ASCII-art rendering of a 3D scene in a few hours, using an existing engine like Godot or Unity (at least if one is already familiar with the engine).
If you want to make a game engine because you think that'd be cool or you want to learn how game engines work in detail, fair enough (I had such ambitions too, when I was young, but you're far further along than I ever got).
But if your actual goal is ASCII-art rendering, there are far easier ways.