I think experts can't tell me which works I will enjoy the most, but I'm not sure they can't say which works are most worth listening to. That depends, of course, on what is meant be "worth listening to".
I agree that "one doesn't need to know anything at about the way motor cars are constructed to decide which models you like the best." But experts may know things that are clearly relevant to the question of which are the best cars. Suppose a non-expert believes that she likes cars A and B about the same after spending a long time reading about them, driving them, and talking to friends about them. Further, experts know that consumers generally like the cars the same, but these experts know that car A has serious recycling problems and that car B allows engineers to cheaply and easily design other models using the same platform. The experts then say car B is better.
The only way the experts' views do not matter is if
the only criteria for determining "greatness" involve general user (enthusiastic listener) enjoyment. There are many TC posts that explicitly call on music theory in determining a work's "greatness". I do not know enough about music theory or history to definitively claim that music theory arguments have little, if anything, to do with the "greatness" of a work. I think that is the crux of my second question.