>>62257146all the time turners were destroyed during the battle in the department of mysteries
going back and bringing people back would not be possible because they know that they died, thus creating an alternate future where they didn't have a reason to go back in time to save them in the first place, creating a paradox
going back and stopping the revival would also create a paradox because without him coming back you have no reason to go back in time
going back and stoppnig him form making the horcruxes would fundamentally change the future, erasing you the moment that you do so because if tom riddle never became Voldemort, the Prophecy never happens, people that died during the war are still alive, people that were born form the survivors of the war never existed, etc etc
>>62257293wat