It's a big metafictional joke. Everybody tells Larry early on how reunion shows are so lame and disappointing and he says no, we'll do this one right. And what he's actually referring to there is the fact that the only way a Seinfeld reunion wouldn't come off tired or desperate or pointless at this point is if it took place on Curb Your Enthusiasm. Seinfeld is such a '90s show to begin with and it wouldn't even make sense in the context of the aughts. There are a lot of big winks throughout the season addressing this point. They poke fun at it most obviously by making the reunion show itself so lame