There's similarities, but gdscript isn't derived from python or built on top of it or anything like that

You can absolutely use c# for everything if you want, but many people find the convenience of using godot's built in code editor and debugger very valuable. Also as an aside, godot uses its own language gdscript out of the box. If you wanted python it would require a 3rd party plugin

yeah but most of them didnt have a big fuckoff dragon