Christopher Nolan's space epic was a dividing film among critics and audiences. It was either regarded a masterpiece and even compared to Stanley Kubrick's 2001, or simply flawed and overly ambitious. Although this is not the director's first attempt at telling mind bogglingly large scaled science fiction stories with an emotional core, he doesn't do it very well in this one. This article discusses the flaws in the film and contains spoilers.
Pacing and length
While there isn't anything wrong with how slow the movie is initially, the third act of the movie is not dealt with with as much patience and is not as long as it should be. By the time the movie is about to end, the story hasn't progressed enough for it to do so in the next thirty minutes. They visit two planets which are both unsuitable for human life and then, you know, Matt Damon happens and it's revealed that Plan A isn't possible. That they need to retrieve data from inside of a black hole so as to solve the 'equation of gravity' and make Plan A possible. So how does this happen? Cooper travels into a black hole with TARS and leaves Anne Hathaway to travel to Edmunds' planet and learns that Time is a physical dimension created by future humans to which he was brought because of his love for Murph and then uses Morse Code to communicate the data to older Murph thus solving the gravity equation, getting shot out of the black hole and waking up in 'Cooper Station' (the science of which they don't care to explain), find that humanity has survived and finally has a conversation with his beloved Murph (for a few minutes.) only to leave Cooper Station and find Anne Hathaway. Who, by the way, has left the human eggs to develop on Edmunds' planet because its suitable for life. (Love - 2, Mathew McConaughey - 0). All that takes place in about thirty minutes.
Characters and Expostion
For the most part Interstellar is a movie that uses real science. Until the incredibly complex third act which requires a lot of exposition. Christopher Nolan is known to add heavy exposition to his characters' dialogues. One of the criticisms for Inception was that some characters were created just to explain the plot of the movie. Now in Inception's case, that wasn't such a bad thing because the movie doesn't sacrifice the heart of the film; which is Mal and Cobb. In Interstellar, by the third act of the film, once Cooper enters the Tesseract and needs to explain everything, the movie seems just ridiculous at that point. The dialogue is rushed and diluted with exposition. At one point Cooper explains that the reason he was brought to the Tesseract was because of "Love, Tars, love". And after that, the movie doesn't even care anymore. Cooper's conversation with old Murph is too short to be realistic. Nothing more than that, no questions about your children, your brother, the new planet, your relationships, your life, nothing.
Moreover, Interstellar's world is too complicated for even its characters. The characters in the movie respond too conveniently that it's unrealistic. Jessica Chastain Murph knows somehow that the answer on Earth to save humans lies in her ghost encounter. How? How? Cooper knows EXACTLY what the tesseract is. He knows exactly why he was brought there, and exactly how he can communicate the data in a matter of minutes and does not react to the Tesseract with fear. You're inside a black hole.
Love: Plot Device
Maybe it means something more - something we can't yet understand. Maybe it's some evidence, some artifact of a higher dimension that we can't consciously perceive. I'm drawn across the universe to someone I haven't seen in a decade who I know is probably dead. Love is the one thing that we're capable of perceiving that transcends dimensions of time and space. Maybe we should trust that, even if we can't understand it. All right Cooper. Yes, the tiniest possibility of seeing Wolf again excites me. That doesn't mean I'm wrong.
Maybe this didn't need to be said? The film ends anyway proving that an emotional connection would be their survival instinct (Edmunds' inhabitable planet, Cooper being brought to the Tesseract).
The movie is still beautifully done but it is significantly flawed. These aren't criticisms of the story but the way he decided to tell it in this film. A rushed and impatient approach to a very complicated concept. But honestly, the film would've made more sense with Plan B.