One of the complaints I hear often is about the quality of what gets published. The sub-text is usually: how can this dreadful writing get published when I can't? I don't have any specific answers to that, but some thoughts are:
a) different styles of writing appeal to different people. Anita Brookner, for example, makes me want to scream because her pace is so slow, but lots of people love her. I loved Horatio Clare's Running for the Hills and was thrown when several people whose opinion I respect said they couldn't get on with it. (Too many sheep, apparently.)
b) different genres of writing appeal to different people. I'm not a fan of science fiction or anything with too much technical stuff in it. Other people love it. Diversity is good and wonderful.
c) different people have different educational standards. Ages ago I read a best selling author - sadly I can't remember who - who commented that his books were read by people who ran a finger under each line when reading. Books aiming for a mass market readership are not going to be written with an obscure vocabulary or lots of literary allusions. Cliches may be cliches, but they are also accessible and familiar.
d) the more you write, the higher your standards become. Once you become a writer you start to analyse writing in a way you didn't before hand. You stop being a passive consumer and become a critic. This is good, because it improves your own work, but I find it makes reading a less simple and straightforward process.
e) different people have different reasons for reading. I read for relaxation and entertainment, rather than to set myself a challenge. But other people have different priorities and for them the challenge of, for example, experimental writing is worth it.
f) different writing appeals at different stages. There are books that I adored in my 20s that I can't read now. The sort of book I like now, I found boring in my 20s. I'm reading a lot of non-fiction this spring, which seems to suit my mood.
g) and yes, there are lots of external reasons like celebrity and good connections and that produce book deals for frankly sub-standard books. And there are certainly books that become best sellers for no apparent reason.
No one really knows why one book sells and another doesn't. What appeals to me won't necessarily to you. If you want to write you've just got to get on and write your own book and stop worrying about what other people are doing.