When someone claims that a certain subject is "understood" or "well understood", one should be careful of reading too much into it. Interesting things happen at the interface between subjects. It may well be that person claiming something is understood is not actually the one that understands it. And the one who does understand the subject may not understand the other suject that the given author is writing about.
My feeling is that the subject of quantum mechanics is like this. Each aspect is understood, but not many people understand all the different aspects. When these different aspects are combined, surprising things may result that some people know but just don't realize are "surprising".
This is what the process of teaching is about- combining together the understandings of different people to combine a unified understanding. It is not always given a lot of respect because people within the system may not see a need for the global understanding. They know what they know and they know in a certain sense what other people know and the system fits together to run the accelerator or detector or even to compute the 3 loop diagrams or whatever. It is a network of knowledge and people have enough information about the interfaces that they can usefully contribute, but don't know many of the insights that the whole picture contains. The negative attitude towards teaching and integration of understanding can be partly self serving worry that they won't be as important once the whole thing is seen clearly and also a real concern that those that spend their time on integration may well not appreciate the depths of the subject and the strength of the network itself may in danger if too many people were to work on integration instead of detailed work within a defined area.