And yet Seinfeld almost didn't happen. The pilot episode of the former NBC show (at the time it was called The Seinfeld Chronicles) was so bad (and it is bad) that it almost never made it to air. Luckily, there were executives at NBC who believed in the show and kept it around, and Seinfeld went on to become a mega-smash hit.
Unfortunately, we might never see another Seinfeld again. We live in an Era of Too Much Good TV. There are many benefits to Peak TV, but one of the major downsides is that you need to be good immediately. There are just too many other good shows to exist, that if your show if just mediocre, people will bail and watch something else. That creates a problem for sitcoms, as they're rarely great (or even good) right away. Seinfeld deserved its bad ratings and negative test focus reviews, but it also deserved to stay on the air and get the benefit of the doubt from NBC. Comedies almost always get better, and just because you're bad now doesn't mean you can't be great later.