Here's the deal: Get Smart isn't funny. And it doesn't have much to do with Get Smart, in any other way, either. It's pretty much just a regular ol' spy movie with some regular ol' jokes in it. This person who is named Maxwelll Smart is just some guy who's pretty nice and pretty humble and a fairly competent spy (except for a couple sequences where he hurts himself in not particularly funny ways), and he fails to be oblivious, which is the real Maxwell Smart's central character trait.
But, again, the main problem is that the movie just isn't that funny. Alan Arkin as the Chief? Not funny. The main villain and his sidekick? Not funny. Anne Hathaway's Agent 99 isn't funny. Not-even-thinly veiled President Bush isn't funny.The CONTROL nerds and the CONTROL jocks: slightly funny. Big scary villain henchman--a tiny bit funny, near the end. Steve Carell as Maxwell Smart has some funny moments, but he averages out at sort of funny. Dwayne "The Rock" Johnson isn't all that funny, but I continue to find him really likeable, so that's something. And . . . I've run out of characters.
Another way to put it is that the movie Get Smart is just a waste of time. I haven't seen them yet, but my bet is that if you're looking for an excuse to eat popcorn while sitting on a cupholder-adjacent chair in the air conditioning, Kung Fu Panda or Wall-E or maybe The Incredible Hulk** would be better ways to go.
**Admittedly, I'm only tempted by the Hulk movie because of its tenuous connections to Iron Man. Apparently I only like to write about movies that I dislike, because I never wrote anything about Iron Man, which I LOVED. Seriously, LOVED IT. And not even in the way I loved Live Free or Die Hard, but loved in it a "This is some quality, lovingly-crafted cinema!"-type way.