I disagree with this. I think it is perfectly reasonable to tell a program that you are considering ranking their program highly because of X, Y, and Z aspects of their program, which are extremely important to you and that you admire about them. You can then continue that conversation by asking them to elaborate further on those areas or asking if there is any other aspect of their program that they think you may be excited about, which you've not had the opportunity to discover yet.
This is actually a useful conversation for both parties. It conveys real information about your degree of knowledge, and thus of sincere interest, in their program. It gives them an opportunity to talk positively about their program to you, as if trying to sell it to you. That clarifies the dynamic that you are not just a supplicant there with hat in hand begging for a seat... but a potentially valuable future resident whose interest they have an incentive to court.
It is as sincere as you make it be, and you can absolutely say it to every program you go to, without being at all unethical. Almost as if you were a professional paying due respect to colleagues who extend you the courtesy of an opportunity to meet with them.