That CURT 18085 is just not what a bike enthusiast would use. You want the kind that does have a tray, but where the arms hold the tires and only the tires, not the frame. One thing in common to all bikes is they have a front wheel and a rear wheel, so tire "arms" will hold any bike.
That sad guy who worked at a bike shop for 30 years, demonstrates that don't trust everyone who works there. No, is not "elitist" to recommend a quality rack over a junky one. Good racks are good racks, bad ones are bad. My "resume" far exceeds that forum poster guy and my advice is to look for the best rack for the money you are wanting to spend.
I have seen a lot of junky bike racks doing poorly at their job on the back of RVs, and have seen quality ones. Even if you have a $12 walmark bike a good quality rack will still be more enjoyable and easier to use and much more functional.