Always write for your audience. Consider their age. How does it effect their reading habits and preferences?
I recently wrote about a critique of my novel that will appeal primarily to adults who were teens in the nineteen-sixties and -seventies - that's my audience for this novel. The critiquer talked about how online life, taking in information in small bites, has made the book publishing industry change what they want in writing style.
Well, first of all, many readers in my audience are not on social media - or they do the bare minimum. Secondly, I started self-publishing because I was a few years ahead of a trend - I was pitching gritty, realistic YA fiction when they wanted the next Twilight. I'll make sure my writing on this novel is tight, but I'm not going to try and fit a trend that may pass. I probably won't get an agent or publisher interested, but I can self-publish.
When writing for children, you need to know what age group you expect to reach.
A talented artist friend, Jo Hans-Stafford, had a picture book of her travels to Europe that she intended for young children, most likely to be read to them at first. She took it to a critique group that was not particularly familiar with picture books for young children, and they wanted her to add more text to each page and describe her journey more fully. I reinforced Jo's belief they were off track with that advice - she'd looked at enough children's books to realize that, for toddlers being read to by parents, just a few words a page is right.
On the other hand, as children get older, they still enjoy illustrated books, but they have longer attention spans and can listen to more information with each picture. Kathryn J. Reed had teachers who enjoyed reading her little stapled-together stories to their younger elementary students. We put eight of the stories together and published them in a nice book.
Not every person of a given age is identical, but knowing the age of your audience gives you a starting point.