One of the more rage inducing things I encounter every once in a while, is this type of memes:
Because there are two things wrong just in the above photo alone,
BUCKBEAK NEVER DIED.
This seems to be the biggest complaint over the time-turners and it baffles me, because people seem to have missed the point where Buckbeak never died to begin with. Even in the original time-line Harry and Hermione saved him.
Rowling was very careful not to show his actual execution so when they go back in time, we'd realized we didn't hear Buckbeak's death, we heard the frustrated executioner murdering a poor pumpkin after finding he had escaped.
Dumbledore sent them back in time to save Buckbeak because he knew Buckbeak has already been saved by them. Dumbledore is no dummy.
To take things a step farther nothing in the original timeline has changed by Harry and Hermione's travel back in time as they followed what they knew should happen and therefore made it happen. So, basically, they went back in time to ensure the present remains as it must be and not to change the past.
A huge difference.
So, once again: nothing in the original time line changed, Buckbeak never died.
It's a time-loop, but one that makes a lot of sense. This is why Harry and Hermione remember both the original times it happened (when they didn't know they were the ones doing it) and the travel to make them happen.
Dumbledore is 100% right in the first meme, because no one can be "saved" from death. Lily & James Potter can't be saved, Dobby can't be saved, Dumbledore himself can't be saved. In fact, you can't even go back in time to prevent Voldemort's rise!
Nothing fundamental can be changed.
Why? Very simple. Because that would create a paradox. Think about it for a minute. Were you to go back in time and save them, that version of yourself that needed to go back in time and save them never existed to begin with... so who went back in time to save them?
But say this wasn't an issue, have you considered THE CONSEQUENCES.
Hypothetically, someone did go back in time to save Lily and James. Maybe it's Harry, maybe it's Sirius. They prevent these deaths. What would probably happen? Voldemort would take over the Wizarding world.
Wait, how did I reach this conclusion? Quite easily. What paused Voldemort's attempts for about fifteen years? The powerful spell Lily put on Harry with her death. So, if we follow this logic, if Lily was somehow saved she didn't put the spell on Harry, she doesn't inadvertently give Dumbledore the years he needed to figure out what Voldemort has done to himself, and how to reverse it.
So the Wizarding world would fight against an immortal, and they would lose. And while dethroning a dictator is definitely an interesting plot line, it's not the story of Harry Potter.
Knowing this, would you change anything?
You couldn't let Hermione use the time-turner in life/death situations. Wizards are a lot of things, but dumb they are not. That's why the time-turner was given to Hermione, the smartest witch of her time who would understand the consequences and not, say, Harry who would've fucked up big time.
Now, we've gotten the whole paradox and keeping-the-time-line intact, but for discussion's sake let's say it's possible to change the past without creating a paradox. Even if it was so, have you ever considered how it would actually, physically be done?
THE THREE CONDITIONS OF THE TIME TURNERS MAKE IT LOGISTICALLY IMPOSSIBLE.
To go back in time, one needs to spin the time turner the amount of hours they want to go back, and be in the spot you want to come the other side of. And then you need to relieve those hours until you reach the origin point. These are the Big Three conditions that need to be met in order to work the time-turner.
It's impractical, not to mention near impossible.
Let's look at one of the things fans say could've been solved with the time turners - Voldemort.
To stop Voldemort, one will first need to have knowledge of where and when Voldemort will be at a specific point in time, as well as be certain he has not yet become somewhat immortal otherwise what's the point. So they'll need to know of the Horcruxes as well.
After we have all these, some poor soul will have to go to that location, and sit spinning that time-turner for days non stop. And what if someone tries to stop him if he's somewhere he shouldn't be? What if someone confuses his count? God Almighty, what if his hand slips?
But say none of these things happen, s/he have succeeded in killing Voldemort! Banzai! Only... now they will have to relieve all these years. And in all actuality they can never return to their original point because now it doesn't exist, so they will probably have to carve a new life for themselves. Oh well, they were prepared for it, I guess.
The point is, these things are highly impractical, and damn near impossible, even without the whole paradox problem. J.K. Rowling was very careful in giving her time-turners obvious limitations and restrictions in order to make it clear they were not an all-fix, though a lot of people tend to forget all those and just focus on the time-travel.
So in a way, I'm glad she destroyed them in order to end that conversation, but she didn't need to because she has taken all the right measurements against it to begin with ;)
*Bonus point: according to Pottermore (or the old Pottermore), five hours is the longest period that can be traveled back without a chance of harm to the traveler.
Thank you for sticking all through this rant if you have, and hopefully you found it informative!