How can an instructor call themselves instructors if they do not have the skills to teach and get out of a spin?
Well a PPL instructor only needs to be able to teach the syllabus. They don't need to teach you how to use a GPS or even what aileron to use to turn left when upside down. Instructors aren't permitted to teach aerobatics without undertaking further training. They are still instructors though. I agree ideally instructors should be able to teach everything but that isn't exactly practical, so you have to go and find the one's that teach what you want, and hopefully teach it well.
The easy answer: it's printed on their license!
EDIT: I've seen it written somewhere that you can only learn from someone with a bigger personal flight envelope than you, so while a students' is very small an instructor with a marginally bigger personal flight envelope can still teach them to what is considered to be a generally safe standard.
If you want all instructors to be highly experienced and highly capable you will ultimately come upon the same problem that is evident in other industries which is that experience is king, and no one can get any because experience is king.