There isn't a lot of imagery described in his books (not that I would see it anyway) but that doesn't mean it couldn't be presented visually while keeping to the spirit, just that Asimov probably couldn't have done it. Good writers and directors could.
If given the Villeneuve or Kubrick treatment it might be very different.
https://archive.org/details/foundationtrilogythe--bbc1973rad...
It's one thing to acknowledge the flexibility required in converting a story from novel to film. It is another to change the entire message, character motives and morals while merely retaining the surface plotlines.
For what it's worth, having read ten chapters of Dune after watching the amazing 2021 film, I can say they did a fantastic job capturing the spirit and the core storyline of the book.
If an experienced film creator made such claims then it’s worth listening. Otherwise these sorts of comments are just noise.
There's lots of literary attributes which may make a series easier or harder to adapt, but, just like Dune used to be called unfilmable for the heavy monologue, length, and nonverbal components, a director with a vision can overcome them.
I believe there was a radio show adaptation done by the BBC.