I think FMQ refers to the process of quilting without feed dogs, so even if you are using a pantograph, you are doing FMQ. I would say that using a pantograph as a guide is the machine equivalent of hand quilting over stencil lines, and who would suggest that that was 'less than' quilting? Some people are artistic and can think up their own designs, and others are not.
Allover designs do take less time, and are therefore less expensive than custom quilting, but that doesn't mean allover quilting is in some way inferior to custom quilting. Sometimes an allover design is what complements a quilt the best.
I would say that there are tiers of quilting skills, but what tier you aspire to is entirely up to you. It's possible that charity has so many people offering their skills, that they have the luxury of going only with custom longarm quilting.
As far as whether you're wasting your longarm's capabilities, of course not. You're doing what you enjoy with your longarm machine, and that's exactly what you should be doing.