What makes a book well written?

Kinda dumb question but also kinda not. I have been off tiktok/Instagram because I could not stand the book reading community. Every other post was : "This book was written by a fifth grader" or "If you read (Insert genre) then you're not a true connoisseur of sophisticated literature" or some other snobby bs like that.

But it also got me thinking. What actually makes a book well written?

To me books are art. Art is subjective and beauty is in the eye of the beholder. But just like art, there are technical aspects to it that are supposed to be technically correct like grammar.

But other than that, why is there an influx of critics saying books today are not very well written and are contributing to a literary crisis ( which makes no sense of how reading causes a lack of reading ability)

Are readers looking for technically perfect peices of work? Are they looking for more classically trained writers who studied literature before they actually pick up a pen?

Here's my theory :

It has never been more easy to publish a book. And like any craft, you have amateurs, intermediate, advanced, and master writers. Well today you don't have to be a master writer to share your story with the world.

So, because of this fact not every book is written at the same skill level especially is very low stakes genres like romance and fantasy which receives the most criticism.

So what is a well written book to your average reader, excluding people who specifically study literature (They're a whole other breed)