Their impressive library of detailed articles in where they factually report on myths and conspiracy theories?
Why are you asking such a vague, open-ended question?
"The sky is blue because other stars reflect blue light onto our atmosphere." How would you rate that, given Snopes' scales?
Do you have any specific examples where there was a concise yet opinionated decision on any published articles from Snopes that don't rely on hard evidence for their conclusion?
Now they are into very fuzzy realms where they are going to have to fact check claims that are plausible. That's hard work. You have to actually... uhh... check the actual claims.
Nobody really fact checks anymore because it's damn expensive. Unless someone gives them a budget for real gumshoe work, Snopes will just end up applying a bunch of political bias filters and lazy heuristics. Facebook could get that with deep learning so I'm not sure why they'd be interested.
You have it exactly backwards. I've never seen anyone give a good reason why Snopes should be trusted. The Mikkelsons were self-appointed "authorities" from the beginning, with zero actual expertise or credentials in most of the areas they opine upon.
Edit: I should add that I view any organization that feels the need to use "truth", "fact", or similar in its name with an extremely jaundiced eye. It's reminiscent of Pravda and "Honest John's Used Cars". Organizations with actual earned credibility don't use names like that, as a rule.