SCIENCE IS SEEKING A CURE FOR THIRST AND I HAPPEN TO BE THE GUINEA PIG: Whether you accept MZS's resolution of the Vulture Sitcom Bracketology depends on whether you consider The Simpsons to be a sitcom in the first place. If you do, and if cultural impact is part of your criteria, that pretty much ends the inquiry, and I rather like Seitz's analogy that we don't discount the overall greatness of the Rollling Stones just because they haven't been brilliant for the past few decades.
If like me, however, you see animation as liberating The Simpsons to do things with narrative, scope, and pace which go way beyond what filmed programming could do, such that it's comparing apples with MacBooks to put it in a competition with Cheers, Roseanne, and The Cosby Show, then not only did Seitz get it wrong but he answered a question which should not have been asked. Especially, as Linda Holmes notes, when ubiquity is used as a metric for quality, and The Simpsons are being compared to shows which didn't have Usenet/WWW vehicles to drive discussion and foster that ubiquity. (And there is no Cheers or Cosby equivalent to Songs in the Key of Springfield.) Moreover, looking at things that way denies the singular talents of the shows' stars -- you couldn't reproduce The Cosby Show because there's only one Bill Cosby.
We don't knock George Washington's skills as a general just because he didn't use tanks and bombers. Same should apply here; Cheers 4ever.