Backbone allowed me to write cleaner code without forcing me to do anything. I still use backbone today. The code tends to be very verbose, but the trade-off is that it is not heavy handed. I never have to "hack" around backbone, it just gets out of my way when I want it to.
This fits my personal preferences, I prefer simple, verbose code. I also tend to prefer lower-level to high level. For example, I don't like ORMs. For me, it is easier to explicitly express how I want the data to be indexed and move in and out of a database as opposed to have an ORM manage it for me... because if it doesn't do it right, its very difficult for me to learn how to get the ORM to do what I want it to do. I also prefer more keystrokes and fewer "things to have to know about" to fewer keystrokes with many things going on behind the scenes that I cannot see. I think I may be in the minority in this respect?
I understand that there may be better frameworks now, but I feel I need to commit to something and stick with it, I think the cost of re-writing things all the time is too high. I think its faster in the long run to use an old framework that's 50% slower than switch to a better framework every two years.
For reference, this is the main project I use backbone on: https://demo.enterprisejazz.com/