Curb and Larry Sanders were different models though. Curb and Sanders both worked because predominantly they were 'real', in other words, no studio audience, no forced lines. In both these shows you didn't have to be funny all the time. because the product was strong enough to go a couple of minutes without a big gaffaw.
Seinfeld was different because it (almost contractually) had to havea funny line in every four. I liked Seinfeld, but it hasn't aged fantastically well. Except perhaps for the Kramer bits...random madness is ageless, it appears.
Also Curb and Sanders had looser boundaries, being HBO and not being bound so much into the whole affiliate scheme the US is obsessed with. It's amazing we have had so many good shows, given there are people who are offended by anything in the US and the companies go out of their way to avoid any offence.
There's a scene in Family Guy where they start censoring everything, and the claim is they have had twenty calls and "as you know, gentlemen, one call represents a billion viewers. We've had twenty billion complaints"
There's more thana shade of truth in that