I've used Ember.js in the past and must admit that it got in the way and the whole team was magnitudes slower than it should be, although I would also see the bad codebase we had to build upon was a big factor of this, so I can relate to that.
But I've never experienced this problem on projects where I'm able to choose my tools. I use Django and Vue.js with webpack and I can estimate the time constraints for each feature accurately using that stack which is most important for me.
Maybe you've used too opinionated frameworks in the past. If that is the case, loosely coupled frameworks like ampersand.js or very flexible solutions like Vue.js will be a pleasure for you.
In regards to the Pareto Principle: The 80/20 rule means that you need 80% of your time to finish those 20% outside the scope of your framework, not 20%, so your observation fits with this.
But I've never experienced this problem on projects where I'm able to choose my tools. I use Django and Vue.js with webpack and I can estimate the time constraints for each feature accurately using that stack which is most important for me.
Maybe you've used too opinionated frameworks in the past. If that is the case, loosely coupled frameworks like ampersand.js or very flexible solutions like Vue.js will be a pleasure for you.
In regards to the Pareto Principle: The 80/20 rule means that you need 80% of your time to finish those 20% outside the scope of your framework, not 20%, so your observation fits with this.