Manhattan is not a god, just a powerful human. He's not omnicient, for instance. Manhattan percieves time as all happening at once, but it's limited to his lifetime and personal experience.
He also "can't control everything"- a notable example is that he was unable to do anything about his ex wife's cancer, and exiled himself to mars because he had been tricked into thinking that he was carcinogenic.
Let's look at the surfer.
Surfer's perception is universal, thanks to the power cosmic. He's able to percieve threats across the galaxy, and know the weaknesses of an opponent innately in fractions of a second.
He can not only look into the past and future of any area he's in, he can travel back, forth, and across (?!) time without fear of paradox. He's thrown an opponent to "the end of time" to get rid of them before.
and healing cancer? Surfer healed an entire planet of a deadly virus on a subatomic level, simultaneously.
collecting yourself from scattered atoms isn't even a novel ability at this tier- there are a LOAD of people with insane levels of molecular control (sersi, for instance) for which this is a non issue. suddenly those atoms are now all bricks, or whatever.
And that's just the SURFER. He's the low man on the totem pole compared to what cube beings, celestials, or abstracts do.