Inception was better, Interstellar was well crafted and took risks, however, it had more problems. While i do hope he tries correcting some of the problems his latest films have had, i'm excited to see what comes next in his filmography.
What kind of problems?
That's not actually a problem with the movie and it's a pity people think it is. That's simply how time travel works within general relativity: closed timelike curves. A-> B -> C -> A. In comparison what we're used to is simply A-> B -> C -> D, that's how it works in the world when there is no time travel, outside of black holes, worm holes, et cetera.Mostly holes in the plot, this can happen with any film, but i think they were too big. The ones that comes right to my head are the paradox where humanity from the future had to save itself in the past, it's a bit like answering that a chiken exists because it went back in time and put an egg in there. By the way, if the answer to save the planet was as simple as a morse code, why didn't humanity from the future simply deliver them to some scientist in Earth?
That's not actually a problem with the movie and it's a pity people think it is. That's simply how time travel works within general relativity: closed timelike curves. A-> B -> C -> A. In comparison what we're used to is simply A-> B -> C -> D, that's how it works in the world when there is no time travel, outside of black holes, worm holes, et cetera.
Humanity from the future could not simply deliver the message, as they only exist because of Cooper and Brand's journey. They exist because Cooper went to the worm hole, because he had the courage to drop into Gargantua and transmit the data on the event horizon, because his daughter was the one who could piece things together, etc. I think it's also implied that the 5th dimensional beings were also the physical descendants of Cooper and Brand, but I'm not sure.
That's the way it happened and thus it can't happen any other way. See also the Novikov self-consistency principle, when applied to rotating universes or billiard balls.
This may seem unsatisfactory, but that is the way time travel works within general relativity, and the movie chose to follow those rules.
ETA: If I told you that you could never kill your grandfather by going back in time, you might respond that this doesn't make sense. Well: you probably can't kill your grandfather even if you have a time machine. Those are not established rules since we don't have a time machine, but they're the expected rules.
I'm not sure it realy works that way, if humanity from the future exists in the future, it means they had to survive in their original timeline from some other way, in the film, the past actualy seems to be dependent on the future helping it. Theoreticaly, going back in time to kill someone who later had a son would alter the future, but what the film presented was more like someone having to go back in time in order to make his parents get together, which means that in the original timeline, his parents never got together, and he never existed, which doesn't realy make sence.
The problem's not realy that the past was changed witht he future's help, the problem's that the film makes it clear that had the future not helped, it wouldn't exist, it's a paradox.
There is no original timeline where his parents got or didn't get together. There's no meta-timeline against which the timeline evolves. He went in the past to help his parents get together, and that's how he was born. That's the only timeline.what the film presented was more like someone having to go back in time in order to make his parents get together, which means that in the original timeline, his parents never got together, and he never existed, which doesn't realy make sence.