Huh, that’s so, it was there last January. It used to follow this paragraph (still there today anyway), which contains a similar criticism with citation:
It is widely used and has sometimes been criticised for its methodology.[4] Scientific studies[5] using its ratings note that ratings from Media Bias/Fact Check show high agreement with an independent fact checking dataset from 2017,[6] with NewsGuard[7] and with BuzzFeed journalists.
So if those are considered fact-based, there’s no need to delve further.