That's a huge plus in my book. Frameworks tend to obscure what the application actually does because there is orders of magnitude more framework code than there is application code, and frameworks tend to be very indirect when going about their business with 12 different layers hit for a simple operation.
As a counter, if you look at the code, there's a lot of DOM api calls littered throughout which obscure what is going on. This could be relieved by pulling out the DOM manipulation into common constructs that all parts of the app use, but then you're creating your own framework/library and might be better off using a battle tested one.
Given how responsive the UI is compared to most modern UIs built in the "battle tested" frameworks & libraries, I suspect the recommendations in this comment are all well and good in theory, but not necessarily reflective of reality in practice.
The app is super impressive!