When I was learning python front-end frameworks django and flask, they both seems archaic as compared to nodejs. django has steep learning curve as well. Creating charts and having real time update using django channels is quiet complex.
I was not aware of dash but while searching for some chart related updates, I came across dash. I was super excited to learn more about Dash.
Dash documentation is not adequate, however its sufficient for you to get started but you need to go through it couple of time. Don’t go through documentation from start to end like a book but find a problem and try to implement it (well, that is the best way to learn any programming language or framework )
To create a web app with Flask or django, and then combining it with interactive JS frameworks, and then incorporating the interactivity with jquery, ajax, and React would take you quite a bit of time and code and this will make application very complex and hard to maintain, however with Dash, this is very easy.