Most quilt binders do not do a very good job.
Bernina used to make one that could take the wide strips for binding quilts, but they discontinued it quite a few years ago because so many people had problems with it. (I don't know about the new Bernina's; mine is over 10 years old!) The only Bernina binder available for my machine is designed to bind clothing (armholes on children's garments, for example, using narrow bias strips).
I bought a Martelli binder at a quilt show. Very difficult to use, so I gave up trying.
My bet is it is not user error with the binders you have purchased; more likely is that they just do not work very well for quilts.
Hmmmm.... Just re-read your post and maybe we are not talking about the same thing. I am talking about binder attachments to a sewing machine.
If you are talking about the Simplicity machine that folds already-cut strips, I have heard good things about it; however, you must purchase the correct size tip for quilting. I think that is an additional purchase.
The Simplicity strip cutter has gotten bad reviews.
Could you post a link to the thing so we can see exactly what you purchased?