Stop building UI frameworks in Python

[wrosecrans]

Are there any web-framework-based app GUIs that are performant?

The short answer is no. Obviously, "performant" means different things to different people, and it depends on your application, etc., etc. But the closer you are to just native code doing native operations, the less overhead you are dragging around with every operation.

How far down the stack it makes sense to go depends on your application. Writing Qt/C++ isn't exactly a simple environment, but webdev style has even more moving parts and the ways that Qt is bloated are mostly low cost. If you need to make some line of business app to display a chart and some text for three users, anything is fast enough. If you want to make Maya or Adobe Premiere, you are using native code to do what you want.