It is like people are unable to picture utopia the same way someone born in the 1900s could probably not picture pocket computers or anything on the internet in full detail.
an important reason very very very good worlds are hard to picture (especially in full detail) is that they are very far away from us in development time. like, i think there would probably be more technological/economic/social development between now and very very very good worlds than between the big bang and now. these worlds would be extremely hard for us to make sense of (though ultimately not meaningless). also, my guess is that these worlds will still bedeveloping; this would thwart attempts to conceive of them as given/finished things
or you might be asking why people find it hard to picture any world that is even merely much better than ours, and not necessarily very very very good or near-perfect. in that case, my comment is less of a response
an important reason very very very good worlds are hard to picture (especially in full detail) is that they are very far away from us in development time. like, i think there would probably be more technological/economic/social development between now and very very very good worlds than between the big bang and now. these worlds would be extremely hard for us to make sense of (though ultimately not meaningless). also, my guess is that these worlds will still be developing; this would thwart attempts to conceive of them as given/finished things
or you might be asking why people find it hard to picture any world that is even merely much better than ours, and not necessarily very very very good or near-perfect. in that case, my comment is less of a response