Scientism is a real thing but I think you're being unfair in blaming this on people who happen to be good ambassadors for science.
In reality, it means stuff like "You should not buy homeopathic cures because it's exactly the same as water."
I'm OK with science being the arbiter of truth when it has evidences.
Edit: Also, in my opinion, Hawking's A Brief History of Time is one of the best books that explained basic ideas of cosmology (and how it is worked on) in terms that laypeople can understand. If that makes him worthy of a special mention of criticism, I don't know what to say.
It was a "scientific fact" that smoking didn't cause lung cancer, for far too long.
Both believing in homeopathy and believing junk science can be avoided with the application of critical thinking and some basic scientific literacy. Because in reality, science is a human endeavour and is as full (if not more) of shady dealings as any other human endeavour. The process gets us further from untruth (as opposed to closer to truth) as it is applied honestly and diligently, but plenty of conducted science is neither, and science reporting doubly so.
But if people are encouraged to cargo-cult "believe scientists always", they're just as gullible as ever.
I understand the scientific process as well as any non-scientist could expect to (ie, in theory if not in practice). I studied physics in college (not that that's some big credential, but I do have some exposure to the idea).
My issue with scientism is it aims to credit "the pop scientists" as an authority rather than encouraging scientific skepticism and scientific literacy. It also promotes science as the only way to glimpse truth, but that's a separate and more complex issue.
Hero worship of scientists as a class (let alone individual scientists, or TV presenters in some cases) as being the holders of truth is not a good thing, but I'm excited to hear your arguments for why it is.