That is an excellent question.
You are absolutely correct in that adjectives and adverbs modify nouns--essentially making what the author hopes to say more precise. :) That is sometimes true, but other times not so true.
What you are running into are trends.
If you look at 17th-18th century writers--the adverb and adjective ruled.
The reason there is a war on them started with readers.
As editors/agents studied why readers 'read and liked' or 'read and liked less or downright disliked' stories, a trend developed.
Readers didn't like reading stories that told them what they should think. Kinda like saying, all the good guys have white hats and the bad guys black hats...so you recognize them from the start as the one you are rooting for. Except that the favored books didn't tell you the guy was good. You, the reader, had to discover it. In fact, the hero/ine was often flawed, not always good...sometimes definitely bad (Breaking Bad anyone?) Does anyone want a book where the good guys wear only white hats? I think not.
As publishers learned what sold, they made 'guidelines' to 'go by'--omit adverbs (see Strunk & White on adverbs--use sparingly) and use less adjectives.
Compare the following sentences and tell me which gives you the clearest picture of what is happening? Does one show the actions of the girl more or does the sentence tell you what to think? There are adverbs and adjectives in both, but one is more subtle and requires the reader to discover what the actions mean. The other tells the reader what to think.
She shook her golden crowned head coyly and then pounded the table petulantly, her pretty blue eyes sparkling, "I'm WAIT-ing"
She tossed her hair back in a slow arc and the silken strands settled around her shoulders. A gold curl dangled over one blue eye. Her lashes dipped, before widening and she peeked up at him. Her lower lip protruded and a tiny tongue darted over it, leaving a shimmer. She pounded the table with her glove and tapped her foot, "I'm WAIT-ing.".
Which made it easier to imagine? While 'golden' shows, 'pretty' tells. "Pretty" is open to interpretation, so what might be pretty to one is not to another. So a good use of adjective is 'golden' because it clarifies. A bad use of adjective is 'pretty' because it tells.
Following on the desire to 'show' versus 'tell':an author might choose to give the reader a choice of endings. The TV dramas that 'fade to black' allow for the Happily Ever After (HEA) types to believe the hero/heroine ride off into the sunset together.
A different take might be that the hero and heroine recognize that each must follow their own paths to find self-fulfillment, so that person would read fade to black as they separate.
A hater might see the fade to black as where the hero kills the heroine.
Three different interpretations so the reader brings something to the story. The same thing is true for adjectives and adverbs. Some give the reader no leeway. Others are interactive.
The real reason people became so hot and bothered by it was because of the bottom line. Fewer adverbs and adjectives tend to sell better to a larger audience. Simple straight showing of the story.
Last, all rules are made to be broken. All guidelines are made to be broken. J K. Rowling used lots and lots of adverbs and adjectives littered her pages. Tell a really superior story and the rules can be broken.
As a fledgling writer, I started by using Autocrit Wizard and reducing my use of many overused words, adjectives and adverbs. My writing strengthened as a result. I am far from the greatest, but I am better.
I hope this has helped. Feel free to ask me to explain anything I did not make clear.