"Fixers" are incredibly valuable, and only a moron manager would squander them (sadly, there are a lot of terrible managers out there).
I remember watching an episode of the new American version[0] of HPI[1], and thinking that it is a SciFi story, because her manager is a smart, fair woman that believes in her, has her back, and takes personal risks on her behalf.
Bad managers can destroy or hamper just about anyone's career. I've seen exactly that, many times.
There are a ton of bad managers out there. For some reason, they never seem to have to account for their terrible performance.
I suspect that bad management may just be the single biggest issue in tech (and many other industries), today. Much as everyone wants to rag on managers, good ones can make a huge difference.