Description is one of those facets of writing that many claim can hook or lose a reader.
If you bury me (your reader) and your characters in description that does nothing to deepen the characters and/or further the plot you’ve probably lost me as a reader. But, if certain facts are necessary to understand the current situation/threat for the MC, such as he/she has red hair and red hair doesn’t exist in this society so the hair MUST be covered if he/she is to sneak out of the city, that description and fact needs to included.
It is a fine line to walk – between too much and too little – and too creative.
Another fine line is needed/not needed description. “It is the end of Chapter 1 and I don’t know what the MC looks like.” [This mainly comes from other writers in a critique situation.] They are right. It is the end of Chapter 1 and no the MC has not been described because what he/she looked like is totally irrelevant to the action/scene/events which occur in that chapter and may not matter to the entire story. Does it need to be included? IMO – no.
I remember in one of my favorite series of fantasy books – it wasn’t until book 2 that I discovered anything about the author’s conception of the MC’s appearance. Did that lack of knowledge hamper my enjoyment of book 1, not in the least (in fact I frequently reread that novel). I had no problem because until the information was presented, it was not relevant to the events of the story.
Another, IMO, descriptive pitfall is the ‘much too creative’ description. I read a story once where the female MCs gown was described as: ‘dripping off her shoulder and pooling at her feet’. Beautiful and creative description, BUT literal me was totally thrown from the story and became completely focused on figuring out how long a dress could drip before the female MC stood nude in a tavern which was filled with men. Every time thereafter in any scene involving the female MC, this was the only image in my mind. I had to quit reading that novel because I found myself laughing through all the scenes which were supposed to be tense.
A creative writing coach urged unique descriptions. The FMC was a single young female living in the city and working in an office building. The coach suggested that the author have this FMC describe the MMC’s smile as being as “wide as a butcher’s dog”. I agree 100% that this description is extremely evocative, especially since I grew up around dogs and butcher shops. But the story was set in the modern world where dogs would not be allowed anywhere inside a butcher’s shop, and none of the background for the FMC indicated ANY familiarity with butchers, butcher shops, or dogs etc. So as a reader who read that, instead of remaining immersed in the story, I would have exited to wonder where that comparison came from … what background the FMC was drawing on to make such a comparison, because to make a comparison the FMC would have been drawing (most likely) on her experiences and if that experience isn’t there the description jars.
Conclusion: Yes setting and description are important to a story WHEN they add to the overall plot and don’t distract the reader.