No one is unteachable. Each time you get on the floor you get a little better. The important part is that you compare yourself to who you were yesterday, not to anyone else.
As Taylor-Sensei always says "If you are in front of me, I'll teach you." There are some members that come once a week. Students disappear around midterms and exams. Life happens. The important part is you make the effort to be there when you can. If you show enthusiam, there is always a place for you in class.