Except that if you take it that way then you're reading things into the statement that weren't made there. "I don't know," means just that: They don't understand, not that they disaprove.
IMNERHO there's really nothing wrong with a simple statement of confusion. It's essentially an indirect way of asking what, as far as I can tell, is an ultimately harmless question ("So what do people like about this?.. Because I don't see it..."). There are, admittedly, a few cases where people make it rhetorically (in which case, ok, yeah, THEN it probably does imply disaproval), but those are the exception, not the rule (and this certainly doesn't seem to be such a case).