"According to the consensus, I should have gone with Backbone.js in 2011 (then Knockout, Ember, Meteor, Angular…)"

The best investment that I ever did was really learning JavaScript and all it shortcomings. The problem with a longer younger colleague's at work is that they seem to learn frameworks instead. They can make cool stuff but from the moment they are in situations where for example "this" does weird stuff, they don't know why or how.

There is nothing wrong with using frameworks - I use a lot of React these days, before a lot of Backbone - but if you know enough JavaScript changing between them should not be a big deal.