AngularJs was a dive into super-highly-opinionated-frameworks. It literally high-jacked JavaScript to the point that it was treated as a https://en.wikipedia.org/wiki/Domain-specific_language (DSL). It was subserviant to Angular.

AngularJS' popularity was the result of the Javascript world seeing a MVVM pattern for the first time. MVVM was already 10+ years old in C# at the time. The pattern worked perfectly for Javascript.

AngularJS was terrible due to how it was implemented, it went overboard on concepts such as Dependency Injected and subverted the concept that the language itself should be able to freely grow on its own.

When the new Angular came along, they corrected these issues, and today with Angular 11 here, It has become a very nice work of art. Does it take a super long time to learn? It depends on where you are. JavaScript itself can be argued to take a long time to master. It's all relative.

Bottom line, if you want a very good front-end framework that allows you to contain state in any component you want (directly) then Angular is for you.