How can I incentivize users to perform creative tasks?
I think the methods you describe (i.e. those employed by Stack Exchange) work for creative tasks as well.

Asking good questions, and providing helpful answers can be considered creative. It's entirely possible that a user can put a lot of effort into an answer only for it to not solve the problem at all.

Whilst it can be disheartening when content isn't as good as you imagined, the feedback given (through upvotes and comments) allows you to improve upon what you've already produced, with the hope that it can be salvaged into something useful. This is essentially the benefit of gamification for sites like SE, by rewarding good content it encourages users themselves to improve and expand their knowledge - it's a learning experience.

So if a user is put off from submitting a recipe because they fear the community will react negatively to it, then maybe it was never very good to begin with.