"The mission" is trivial at that point though. They have a HANGER FULL OF SPACESHIPS orbiting Saturn, it shouldn't be that hard to fly a bunch through the wormhole to pick up all of the people who went through including everyone on the planet of Anne Hathaways. Oh and those space stations look pretty nice, keep building them and gradually get more and more people off Earth until it recovers from "pollution".
You know what I want for the future of humanity? NOT ORBITING A FUCKING BLACK HOLE. This was the biggest WTF for me, if the planets are orbiting it then where is the warmth and light coming from when the neutron star orbits away? If the planets are orbiting the neutron star then why did they go so close to the black hole? It just doesn't sound that friendly.
For all everyone knows, they sent a few ships through that wormhole 80-100 years ago that never came back. I doubt sending any more through seems like a good idea to them. Also, the warmth and light are coming from the accretion disk of the black hole. The black hole is the only thing making the planets viable in the first place.
The whole leaving your daughter to die after seeing her for 2 minutes is pretty ridiculous, though. While its been 80 years for the Murphy, its only been a couple weeks for Cooper.
The reason they didn't send anyone to get the Anne Casthaways is that the time dilation for her trajectory around the black hole to reach the Wolf's planet put her arrival at about the time that Cooper dropped out of the wormhole.
No one ever planned on staying on any of Gargantua's worlds forever; it was only intended as a life raft for as many of Earth's people as possible until they could find a permanent new home.
The mistake that Brandt/NASA/Cooper made was thinking that the wormhole was put there to provide a place to go, as opposed to being placed very specifically there by future humans to allow for current humans to get to Gargantua in order to find the readings/measurements needed to "solve" gravity. Gargantua was the target, due to its very rare characteristics (old, huge size, dense mass, very rapid spin to allow for crossing the event horizon without being torn apart by either the rising or falling singularities "inside" the black hole, get the information they needed, reach the tesseract, and transmit the info back to the past.
Thank you, thank you, thank you for someone getting that 5th dimensional beings, for whom "time is like terrain", don't experience paradoxes.
Cooper left in the end to honor Murph's wishes, plus he at least symbolically completed what he wanted to do as best could be done. The young daughter he had left was gone, though, and the ending also allowed him to close the "pioneer" loop. Would it be what I, or any other living human would do? Maybe, maybe not but in that moment he was ultimately fulfilling his desired destiny an explorer.