If you can bring yourself to stop expecting a masterpiece, especially on the early drafts, that will go a long way in helping you get the story out. No one's first draft is perfect. That's why drafts are a thing.

My early drafts are utter crap, but I revise and revise (I'd been working on my longfic for almost 2 years before I started publishing) until they are closer to what I envisioned. Those writers you are comparing yourself to have definitely done some editing. And sure, some people are naturally talented, but a lot of those writers put in a lot of hard work.

Look into "morning pages." That helped me personally break out of a slump because it forces you to write, even when you don't want to, even when it sucks. And for some people, getting the words down helps more flow.

And if you haven't talked to someone about your mental health and that is accessible to you, that may be a good step, too.