Just a guess, but you'll likely always feel there's no structure if you keep hopping instructors who do things differently?
Have you tried directly asking for their teaching plans/structure, or failing that, setting your own? Past a point I was the one telling my instructor what I wanted to do or work on that day, they might not always agree but the conversation was there.
(by 20 lessons, in, I don't think (imo) they should have anything 'new' to teach, it should be Practice Practice Practice.