As long as they tell good stories with good characters, people will watch.
And because of that, it would not hurt them the tiniest bit to make it part of the Prime universe.
But, again, what's the "Prime Universe?" The original TV series upon which all the derivative shows are based? Or are you including the derivative spinoffs as well? In that case, you're talking about a universe created and maintained for the spinoffs
, not for the original. That would be like insisting that all future Sherlock Holmes productions be based on the derivative films featuring Basil Rathbone and not purely the original Conan Doyle stories.
There's nothing "prime" about the Trek spinoffs. No matter how good (or bad) they are, they are derivative
works. As are, for that matter, the TOS feature films. They are no more valid or "prime" than any derivative of Star Trek, including the Abrams films. In fact, though I don't actually like the Abrams films, I consider them more "prime" than Voyager or Enterprise, because, featuring Kirk and Spock and the Enterprise, they're closer to the original material.