it’s literally just the personal website of a random guy who doesn’t even have any background in journalism or academic research;

Really? Cause this sure sounds like you're wrong:

Dave M. Van Zandt obtained a Communications Degree before pursuing a higher degree in the sciences.

he’s a healthcare worker.

The majority of college graduates eventually end up with a career that wasn't their original field of study. And lots of people have hobbies; quite a few are really good at it, particularly when they studied it for four years.

Media bias fact check has no credibility

Hunh. You might read the "reception" section of their Wikipedia article, which basically boils down to "it's not perfect but it's pretty darn good, and when they compare it to academic research on the sites in question, it's pretty accurate".