I buy some small quilt kits and haven't had a problem. I also use a good muslin as backing after buying a cheaper one before and learned my lesson. I don't have a problem with sewing through it but then I hand piece and hand quilt all of my mini quilts so maybe I'm just use to it.
But I do have a problem with your post...I think you should tell CT about your experience as it is unfair to post it here and not give them a chance to make it right with you. This is just my own thoughts which probably should be kept to myself.
Another thought...if the quilt top is finished could you sell it to someone else to finish?