Usually people can get over prefix notation fairly quickly once they realise that it's just more or less treating everything as a function. Main thing about it is that it's a lot faster for the computer compared to infix notation. It's why I use it myself. Postfix notation is even faster, but it does get a bit less easy for humans to follow and also it lacks certain formal qualities I like about prefix notation.
I'm not sure I'd say Narrat is a Ren'py alternative, I think it's aiming more for the Twine space but with its own twist on things.
That's fine.