It's 100% completely usable for that purpose. To the point where I'm internally using Godot as a backend for my engine, using it for rendering/system events.
It's also really good for a hybrid setup where you use their editor to design scenes, and then you can load/instantiate the scenes at runtime how/when you want. Or, just programmatically creates scenes yourself from code. You can really do whatever you want.
You can do everything from C#, rider launches the player only for debugging if you want. The only thing you probably do want to use the UI for is for... building UIs.
It's also really good for a hybrid setup where you use their editor to design scenes, and then you can load/instantiate the scenes at runtime how/when you want. Or, just programmatically creates scenes yourself from code. You can really do whatever you want.