It is a huge stretch to call transitioning from angularjs to angular learning a new framework.
At the time that’s precisely how it felt though. So much so that I personally felt it wasn’t worth it relearning everything. Had shipped several projects with AngularJS at my very first dev job, and have never written a line of Angular v2+
It confuses me when people talk about frameworks as being totally different. They solve the same problems, slightly differently. It’s not a big lift to learn a new one if you are familiar with one or two already.
That might be generally true for frontend frameworks these days, because they’ve all converged around the same ideas. But in the mid 2010s, Backbone was very different from jQuery, which was very different from Knockout, Ember, ReactJS etc. certain frameworks embraced certain programming paradigms, others embraced others.
Some of my colleagues didn’t make the jump. Those that were the most into AngularJS back then are still writing Angular apps today.