First of all, there are plenty of different data structures in Common Lisp. I don't know any Lisp resource that will tell you or encourage you to use lists for everything. For example, I think all the major Common Lisp books encourage you, explicitly, to use the advantages of different data structures.
Secondly, there is no contradiction between the usefulness of structs and the usefulness of nested lists and the ability to reach directly into them. But structs are no more a universal solution than lists are, so I don't know why you would be so hung up on them---in particular since we aren't discussing a particular use case.
I think the "unreadable monstrosity" thing in its various forms boils down to non-lispers not being used to car/cdr. That may be a fact, but it isn't an argument (and it takes about 5 mins to remedy).
Secondly, there is no contradiction between the usefulness of structs and the usefulness of nested lists and the ability to reach directly into them. But structs are no more a universal solution than lists are, so I don't know why you would be so hung up on them---in particular since we aren't discussing a particular use case.
I think the "unreadable monstrosity" thing in its various forms boils down to non-lispers not being used to car/cdr. That may be a fact, but it isn't an argument (and it takes about 5 mins to remedy).