I think it depends on how you quantify "simple." If you refer to simplicity as a small framework or library with very little moving parts, e.g react or sinatra, then that's one way to arrive at a definition. However, complexity in a designed problem arises when you need to take a large variety of 'simple' components and mesh them together to solve a problem.

In this context, I'm defining simplicity as low barrier to entry and/or easy to understand ideas. I think of myself as a fairly average developer; that I'm not wholly intelligent or skilled. I want a framework that bosses me around and tells me what to do.

Accomplishing simple tasks like mapping JSON returned from Rails to Ember routes and rendering that data into a table was very easy for me to understand and do. The simplicity I'm talking about was the setup, generation, and mechanics of the process. Ember, as another commenter pointed out, is not simple internally. It is glued together using evil magicks as far as I'm concerned. But I'm happy about that because when something does break, it means that I'm doing something that is going against convention or that something is truly broken.

As far as the former, then I need to learn the convention. For the latter, then I need to post questions in forums, hit up IRC, etc. But the positive aspect about the second process is that my project is already fully set up and I'm comfortable with my framework enough that I don't feel completely out of water.