The question I have about this sort of thing (and I have recently worked quite a lot with something similar in asp.net/C#, and, frankly, prefer Python even without the “built-in” GUI support) is: at what point does it become easier to just write the HTML/js/CSS/yaml/XML/whatever than it is to figure out how to write the equivalent in Python and have the jit spit out for you the precisely correct well-made code in several other languages, that can be edited and re-generated from source to make changes. I’m not trying to be a spoiler of fun, here. My point is, just like any act of translation vs. original writing, writing in any well-understood language is more likely to be clear and understandable than purposely writing in a different language then translating it, even if one understands both languages equally well, unless it is as an purely academic exercise.
FYI, when I am working on web projects, my go to stack involves Flask with Jinja2, or sometimes React (depends on project needs and customer demands — sometimes people need the new hotness). Fast, quick to set up, easy to deploy; most of the real work is in architecture, design, and business logic (as I feel it should be).
All of that said, if there were a Python library that I could do all the above in without having to, e.g., think in React whilst writing in Python, I am completely for it.