I think this season, probably the last I'll watch on Netflix for the foreseeable future since my Netflix subscription is due to run out, caps out my understanding of “The Crown”. It's a solid-ish season, but has provoked controversy amongst Royal experts because Charles is portrayed as such a dick.
I'd say this season is primary the friction between newcomers (e.g. Margaret Thatcher and Diana Spencer) and the existing Royal Family. This is where the friction we've started to see in Season 3 (e.g. The Queen's neglect of Charle's emotions) kind of result in consequences (e.g. Charle's explosive outburst at Diana and Diana's subsequent offscreen in-real-life divorce and death).
The Royal Family as portrayed here look realllly outdated. Like why-do-we-have-a-monarchy outdated. I would keep in mind this is a show produced to sell streaming subscriptions first, and historical truth comes second in priority to generating revenue for Netflix. Even so, there's enough real crumbs to make the show enjoyable (and to make us really hate Charles).