Television

My head canon:

He was, but didn't know it until grief and anger pushed him beyond what he thought his limits were.

Kryptonian physiology isn't really clear in the movies, and it's barely given hand waves in the comics. But humans are often unaware of what their real limits are. Until we get hit with a strong emotion that bypasses our conscious minds and spurs us into action.

Supes, while extremely powerful, hadn't faced that kind of loss at that scale before (in the movie at least). He might never have seriously tested his limits (and didn't on screen), and may even have been scared to test his limits

Remember, supes, Clark, grew up hiding his powers, they made him different in a bad way as much as good way. Why wouldn't he fear discovering even greater power than he thought he had?

So, whatever the equivalent of adrenaline and cortisol kryptonians have could have been the catalyst. He holds himself to a lesser power all the time because he wants to be as human as he can be. When the chemicals get dumped into his bloodstream, while his mind is reeling with grief, that self inhibition gets abandoned.

There's even an argument to be made that when he took off, he wasn't planning to change time, he was trying to escape his perceived failure, running to a way to avoid the grief and pain. With that, he unconsciously flees to the one direction that could give him relief, backwards in time.

Now, it's obvious the writers meant him to be doing it on purpose, but it's never outright said to be the case, so we can graft head canon on fairly freely.

But, even if it was clear he was intentionally time travelling (or just reversing time for earth only), that would be a power he would carefully and cautiously use. For him to have know he could do it implies he had done it before, at least once. So, supes being a fairly smart dude, but would be unlikely to tamper with causality casually. Then, with that being the case, him resetting events immediately after they happened, in a moment of grief and anger makes more sense. He was being driven to the extreme and chose to use his most dangerous power because the death toll was just too high.

So, even if we take the writer's events that way, supes would still have had good reason to not go too fast in the initial attempt, because of the risk of it. He would have had to reach similar speeds to have caught the rocket on the first go, risking greater harm. So, he doesn't, but the consequences of that choice hit him hard, and he abandons his restraint to save those he loves, and the world.