Every once in awhile I read reviews of SNL. Almost never do the reviews say "it was OK". Unless it is a review by a frequent viewer, they always say something like "SNL is great again!" or "SNL sucks now". Usually these reviews are from people who never or rarely watch the show, and only remember it from 5, 10, 15 or even 20 years ago. These types of reviews have been the same for as long as I can remember. The periods that people now call "classic" frequently met with poor reviews at the time.
One thing to remember is that the show is an hour and a half, longer than most any other TV show. It is hard to fill such a long show with consistently funny material. It is also hard to make every episode funny. Therefore the show (like most shows) wavers between great and awful, depending on the sketch or episode you are watching at the moment. To judge an entire series on one episode (or part of one) is a mischaracterization.
I've watched SNL for most of its life, and although it has ranged from hilarious to horrible, I would say the average show is "pretty funny". The bottom line: there's nothing better to watch on Saturday night, so until there is, I will always watch SNL!