This doesn't rule out going backwards in time.
It only supports that "an effect cannot occur before its cause".
Wee could still change the future (or the present) by sending a "cause" back in time and wait for the effects.
Anyways the future would seem pretty empty if you were the only thing sent there, and any changes you made the rest of time would have to catch up to see.
But playing around in the  past, that you think wee would have more interest in.
Wee could fix some BIG mistakes mankind has made and set the course for the future.
And if it don't work just go back and change it.