supervision

I saw (not completely) your opinion about the lack of private supervision today. I very much understand that intuitively.
A. I would just be happy to know if it was like this for all generations and if not, what changed, because the prophet mentions that only when they sinned were they punished by other nations.
on. Does this contradict the tenth principle of Maimonides?
C. What is determined on Rosh Hashana?