(spoilers)
In Interstellar, Cooper puts duty above all. He is willing to leave his family to do what is best for them and the world. When he leaves to go on his mission, Murph is upset with him because he is leaving. He is unable to reconcile his relationship with her and has to leave without a proper good-bye. This scene clearly shows his ability to detach himself from others as he focusses on duty. As he drives away, he looks under the blanket in the passenger seat, this is because when he left the last time, Murph had hidden under the blanket. He was hoping that maybe she had snuck along and they could have a proper departure. This along with his crying shows that he is not detaching himself from his emotions. He is not coldly leaving his family without thought, he is doing what he doesn't want to do because he knows it is necessary.
Coopers ability to detach is seen again when he goes into the black hole. Brand realizes that he is leaving her, she starts crying and telling him not to go. He looks up at her and says 'Detach' before detaching his ship. He again chooses to focus on the mission and breaks ties where he has to.
Brand is also focussed on duty, she leaves Earth and leaves her father to find a new place for humanity. But it turns out she secretly wants to be reuinted with Edmund, a person who left before her and who she was in love with. She was focussed on duty but not to the same extend that Cooper was. When they have to choose which planet to explore, she tries to get them to go to Edmunds planet. She knows she is being biased because of her love for Edmund but she feels that her connection to Edmund could be used as a guide. She goes on to explain that love is a force in the universe in that it can draw people across space and time similar to how gravity draws matter together across space. Where Cooper focusses mostly on duty, Brand allows for peoples connections to be involved in deciding what action to take.
Mann also left Earth out of duty. He chose isolation and loneliness to search for a new place for humanity. But over time he came to regret his decision. Eventually he quit caring about the mission and only wanted to be reunited with the people from his past. He even went so far as to sabatage the mission. He did a complete 180 and put his desire to be with people above the mission.
When he tries to sabatage the mission so that he can return home, he is essentially dooming the same people he wants to be united with. It is a purely selfish act. He knows that the mission is necessary for the future of humanity but he simply doesn't care, he just wants to be around people again. He tries to blame this on a survival instinct that he ascribes to everyone. He believes that everyone would act the same way in his position.
His decision is mirrored in Tom's choices back on earth. Tom refuses to leave the farm and let his family get medical help. His decisions are purely selfish and Murph needs to burn his crops to rescue his wife and son. Tom's decision to stay with the farm while his family suffers may be due to his survival instinct which leads him to hold on tightly to the past.
Brand compares love to gravity during her speech about love transcending dimensions. The comparison can be seen when Cooper leaves Murph, as he drives away he is being pulled back but he has to exert force to escape. The scene of him driving away cuts quickly to the rocket escaping the earth's gravity to highlight the connection. The desire to be with others is a constant force in society and something that isn't easily overcome. The pull is also what influences Mann to try to come back to Earth and what draws Brand to try to get to Edmunds planet.
Black holes are the ultamate expression of gravity, they are where gravity has complete control over matter. When Cooper leaves Brand to fall into the black hole, he is coming back to his family and is experiencing the completion of his duties. Even though he is separated from Murph, he is able to help her from a distance in the tessaract. His sacrifice was to be able to help her but at the cost of not being with her. While he is in the tessaract, he has a breakdown and tries to tell Murph to tell him not to leave. All of the planets have turned out to be duds and in that sense the mission has failed. He breaks down similar to Mann and regrets his decision to leave but he doesn't abandon the mission. He realizes that he can give her information for her equations.
In the end, when Cooper meets up with Murph again, they have a short reunion but she asks him to leave so she can be with her real family. The consequences of his actions are real and the end result was that he was not a part of her life. She had her own family and her own life separate from him.
Loving people from a distance is possible and sometimes it is the selfless thing to do. Being able to detach yourself from people for their own good is sometimes necessary. Some examples would be leaving a bad relationship, your profession requires it, defending against a foreign invader etc.
There have been times when I had to work away from home and it was difficult. Having a place where you are connected to is very healthy and shouldn't be lightly abandoned. It was important for me to get out on my own when I was younger but I also saw people loose everything because they left their families. I saw people develop drug addictions, I saw them cheat and damage their marriages and I saw them lose the money they were working so hard to get. I don't concur with people leaving mariages simply for money, although some jobs require it. I also saw foreign workers who were separated for years to make foreign income. I think losing a healthy family is never worth the extra income.
Sometimes movies like to push the idea of putting duty above family. It is possible that this is just military recruitment which is commonly done through hollywood. The movie 1917 has a scene where a soldier is close to completing his mission and he meets a beautiful girl with a child and she asks him to stay with her. He is tempted but chooses to leave her to focus on his mission. This messaging seems similar to the detachment ideas in Interstellar. Interstellar came out around the same time as the Martian which seemed to be trying to make space exploration seem appealing and adventurous. Maybe Interstellar was simply trying to motivate people to volunteer to go to Mars which seemed close at the time.
In the movie though, Interstellar seems to be looking at attachment in the context of a dying world. What forces will have to be overcome to get people to focus on duty over attachment. Apparently burning the food supply works and peoples connections to eachother is a barrier. The movie leaves exception for attachment through Brand with her more balanced approach. In the end the movie presents some interesting ideas about attachment. I am not sure if it takes a clear position but at least it provides some ideas think over.