I there's alien life out there, and if Earth was going to be devastated by disaster tomorrow, I don't expect them to help us.
So I don't see a problem with the Prime Directive forbidding it. It creates more problems than it solves. It's shown in Homeward. One guy was so overwhelmed by the Enterprise that he killed himself.
"The Prime Directive is not just a set of rules; it is a philosophy... and a very correct one. History has proven again and again that whenever mankind interferes with a less developed civilization, no matter how well intentioned that interference may be, the results are invariably disastrous."
He says an even more important thing: the Prime Directive is supposed to protect THEM. Whatever they do, eventually they are responsible for the fate of the civilization.