Why do we use much prettier but not much interesting?

Question

Here is the passage from the text I've just read:

I think this material is much prettier than that, don't you?

Well, the design is more interesting and the colors are brighter.

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I wonder, can we say much interesting instead of more interesting in this situation?

It says much prettier but then it says more interesting which confuses me a bit.

Thank you for your help in advance!

Answer 1

"Much" is an intensifier, an adverb which can modify a comparative adjective like "prettier". "More interesting" is a comparative adjective and you can intensify it: "much more interesting".