I guess it depends on the goal. My opinion is that reading hard books at school simply turns people off reading completely. If the reading is fun there's more chance students will carry on reading.
So if the goal is "teach kids that reading is fun. So they do it. Which means their ability to read goes up" , then yes, the books should be more fun.
(We read a Spike Milligan book, which certainly engaged the class more than Wuthering Heights did.)
On the other hand if the goal is to understand "literature", then books with themes and character development and so on is necessary. And of course can put some kids off reading for life.
The thing is, most of these books people are complaining about aren't actually 'hard books', especially when read at a chapter or two per week with a teacher guiding you through all the major themes. The goal isn't to teach kids that reading is fun, it's to teach them critical reading skills.
There is something to be said about reaching the students where they are, but we already dumb down things too much to allow the slower students to keep pace. They can learn about reading for fun in remedial reading classes.
But I remember when my niece told us they had them reading Nietzsche. Her main takeaway seemed to be that they were Very Smart because they were reading Nietzsche. She didn't have a clue what she was reading, so if any of it stuck with her, it was probably as likely to be misunderstood as understood.
Engaging students' attention, even if they aren't ready to fully grasp it, is great exposure.
Forcing them to scan their retinas over black-and-white patterns for hours, not so much.
For me, Gatsby was... not entirely terrible. It was mostly a waste of my time, but looking back I can see some of the themes were at least somewhat worthwhile.
Portrait of the Artist as a Young Man was an absolute waste of my time. If Joyce is worth an adult reading (which I doubt to this day), then don't make high school kids read him.
Possibly, good books hit different at different ages and can be appreciated at each of those ages for different reasons.