There's a tension between teaching pure JavaScript - which provides less instant gratification - and teaching more powerful frameworks - which are more likely to motivate people to keep learning. Being able to build something quickly and show it to your friends is a huge win, and immediately boosts your confidence.
For example, our core team frequently debates whether we should continue to teach jQuery before JavaScript (there are advantages to both). In the real world, people use jQuery. But it's important to understand how jQuery works under the hood, and use jQuery for convenience - rather than as a crutch.
We're expanding our JavaScript challenges to make sure new coders are comfortable with the fundamentals of JavaScript and programming in general.
Regarding things you can do outside of FCC to become a better developer, I strongly recommend contributing to open source: quora.com/What-is-a-step-by-step-procedure-to-bec…
And of course, the advice I give like 20 times a day: code every day and hang out with other people who code.