There is(are) editor(s) who are resposonsible for content issued under their banner. Most reliable "entities" post a disclaimer that the foregoing is the author's opinion, offered for contrarian view, and not that of the "entity". But, SA didn't (doesn't) do that.
What good is such a site that serves only to confuse, rather than clarify? It's like one author saying that the market could go up and another saying that the market could go down --- we all know that! But, what we want to know is, what is your CONSENSUS opinion and why.
Morningstar doesn't do that; Fidelity doesn't do that --- they both have authors with dissenting opinions, but they scrub the overall content to present a consistent view for investors. SA does not and THAT's why they are unreliable.
Morningstar, Fidelity, and Seeking Alpha are very different from each other. I am surprised that you think Morningstar and Fidelity present their opinions in similar ways. This is a big world, and there is room for many different types of content providers.
Seeking Alpha says, in "About Us": "Seeking Alpha gives a voice to over 4,000 contributors".
And they have a page where they explain in detail how anyone can become a contributor.