The Germans regarded solid fueled rockets as inherently unsuitable for manned space flight because, like bottle rockets, they cannot be controlled by throttle or shut off once ignited. The complexity of the Shuttle design also created more modes of failure. In retirement, the German engineers grimly concluded that the Shuttle would kill people.
And, as you point out, in search of new missions, NASA lost its focus on manned space flight. Not once but twice, the organization made operational decisions that killed astronauts.
Moreover, NASA's grip on climate science has led to perverse consequences. NASA emphasized the creation and analysis of vast streams of data from its network of satellites and ground stations. This led to better short term weather forecasts but skewed climate science toward comprehensive computer models.
NASA scientists were repeatedly embarrassed by the more accurate projections of old style meteorologists who focused on cyclical patterns instead of bulk data modeling. NASA's answer was to shut off most of the funding to the critics and marginalize them in the scientific community. And, as you point out, NASA has been a relentless promoter of global warming.
Without the clear and compelling goal of the Moon race, NASA developed a dismal record of colossal waste, bad engineering, dead astronauts, and dodgy science. Mercifully, private enterprise seems poised to resurrect American manned space flight capabilities.
The Shuttle accidents were entirely preventable. 1) do not launch the shuttle if it is covered with ice sickles. 2) Use the good foam not the environmentally friendly foam. Problem solved.
Well, except for overstated (way overstated imo) emphasis on German engineers, that is also a great post. As best I understand from contacts made over the years, as well as news reports and studies, there were many American engineers and scientists upset with the Shuttle program for those reasons.