GDScript is pythonesque enough to where that's alright. By having made their own scripting language it allows for it to flow better with their engine, at least that's my opinion.

I used GDScript and didn't have any issues with using it, I'm sure everyone wants to reuse the millions of Python libraries available but they're not built for Godot. However, using GDNative I'm pretty sure one could put Python support into Godot, as a Godot native plugin that then runs your Python code. It wouldn't be as efficient as just using GDScript though.