Hi Dave,
Let's say that you are looking at it from hindsight and they were looking at it from the position of being in a relatively comfortable position through about 1942, and were increasingly in a panic after that. Getting Herr Hitler to approve planes to REPLACE the Bf 109 and Fw 190 might have been problematic since he was being fed reports that said they were winning with these exact assets.
It might be a case of nobody wanted to be the messenger that got shot and it might be that the guys writing the reports wanted to not be shot together with the messenger. I'd bet the reports Hitler got were rther carefuully scrutinized before he read them, but I wasn't there.
I'm reading between the lines here, and well might be wrong. I am also recalling the number if German General who were executed as being a rather large number. So, if you made General, you didn't exactly have any job security. Seems like they tried to fix it with incremental updates to the Bf 109 and Fw 190. Almost nothing else made it into fighter production except the jets / rockets, which could safely be recommended as new technology superseding both the pistons in terms of performance (if not range).
Now Hitler executed a number of generals, but that was late in the war, earlier he usually only dismissed generals with whom he strongly disagree e.g. When General von Sponeck was sentenced to death by a military tribunal in early 1943 for disobeying von Manstein the sentence was commuted by Adolf Hitler and reduced to seven years imprisonment.