You Samuel, should know best, that application functionality cannot be isolated from general OS bugfixing. As we know, it often looks like: application z needs functionality y that can only be implemented if component x is rewritten and requires w to be fixed in kernel. You cannot just "make z work", unless you wish to hackplement it.

So application or rather target-oriented development may look great on paper, but in reality it is soon bogged down into general OS development, that we try to do nowadays.

Finally, you should know that devs are doing here the things they want/are interested in. How do you propose forcing them to work on something different?