Well time travel is not completely useless, events could be changed for the better of mankind, abid that the alt universe Thoery is true. But who's to say one alteriation will lead to a more devastating out come further down the line. But time travel can also be used for selfish reasons like winning lottery as such. Or predicting the future. Meaning that you would travel forward in time bring back knowledge to moments after you moved forward in time and use that information which can save mankind as a race, or also for selfish reasons again. However this also relies on the alt universe. But it leads to the biggest problem, who would we trust as the saviour of the human race in that event or would do the complete opposite.