Well, the iPhone X does happen to have two rear-facing cameras. So this is probably going to be a bit of an oddball suggestion: Hit that 2x zoom button in the Photos app to switch to the zoom lens, and see what happens. If the streaks go away, than you're in luck, because you just narrowed the problem to the optics of the wide-angle camera. Of course, this isn't actually a solution to the problem -- but until you can get it properly fixed, it at least allows you to take passable photos with that zoom lens.
If this turns out to be the issue, (and of course, as Vine noted, if we are assuming that the obvious things you've already checked include a proper cleaning of the optics and removing the iPhone from any external case you might have on it) than you will almost certainly have to go to an Apple Store to have it serviced. Just try not to be too offended when the first thing they do is whip out a cloth and attempt to clean it. 😉
Good luck!