Your first draft is never a waste of time, and finishing your project is
never a waste of time. Seeing how things fall together at the point where you say "This version is done" is absolutely invaluable for any second drafts, third drafts or rewrites. I really don't want to sound mean, but stopping your first draft because it's full of holes, or because you know you have to rewrite it or you spilled nine French 75s on it or
whatever is a really good way to get stuck in a never-ending cycle of "first drafts" that are never complete enough to
warrant further work.
If your goal was to get to 50,000 words,
get to 50,000 words. Then your next goal can be "use these words to make something better next time." Beyond anything else, a creator's mantra is
finish what you start.
Edit: Oh, and so we all get our dose of cheerful-Naril, 32,000 words! Part II starts tomorrow! :3 This story is probably going to be around 80-90k words for the first draft. Maybe I'll finish by the New Year! That would be fun.