Ok, fair enough. I agree with you about adverbs. They’re no substitute for the right verb.

And it was certainly more than one person’s opinion that writing should be concise.

I just don’t know if you can say that Twain disparaged adverbs specifically- as opposed to advocating for conciseness- and the article is about people hating adverbs in particular.
You can be vague and long-winded without adverbs.