The problem with these sequels

Make a movie. If it works and it's funny and people love it, sit on it for a decade or two. Like a good wine, it will only get better and more valuable with time. Give the world time to build some nostalgia around it. If possible, wait till it becomes something of a cult movie. Then, to prove how good your movie was, make a new movie explaining how many things could've go wrong if only done differently.
This, for me, is Zoolander 2 in a nutshell. And not only Zoolander is to blame here. The same thing happened with Dumb and Dumber and Anchorman. Everything that could've gone wrong the first time is shown in this alternative universe where it seems the gag reel have made it to the theaters.
Do we really need to hear Lloyd Christmas's "most annoying sound in the world" again? The first time was an ad-libbed and unscripted gem. Maybe the fact that it was improvised is what makes it so good.
Do we really need to see Anchorman's news team in a brawl again? It was funny because it was over the top and out of the blue. No need to do it again waaaaay more over the top. The surprise factor also disappears when you see these movies constantly homaging themselves.
I get it, some people like references. But if you see the reviews you'll find that people prefer something fresh like the first time around.
Zoolander 2 is the worst in this regard. One after another after another recycled bit. Hey, remember how Hansel loves orgies? Now he has a steady orgy relationship. Hey, remember Mugatu throwing his latte at his assistant? That's also in here, but slightly longer and over the top. Remember that magnum could stop a shuriken? Now every *beep* person and their mother can do that too. Oh, and with a beam, because that's what the first one was missing.

Good comedy is all about knowing when the joke is over. And the joke was over when the first movie was over. Next time don't wait fifteen years only to milk that nostalgia cow. Or at least work a little bit on it during those fifteen years. Just a couple of hours, every once in a while.