As an example of this, I had to build a management interface for the backend of the project I was alluding to above; itself a web app in its own right. Written entirely in Python, with HTML templates, CSS and JS and a bit of SQL with no "web frameworks", no other dependencies except nginx to proxy requests to it. Easy and quick to develop (a couple of days), and very unlikely to suffer from software rot, unlike a web-framework based system - Python (at least since the Python 3 debacle) has excellent backward compatibility, and basic HTML, CSS and JS likewise.

What it did lack, though, were fancy widgets and other decorative bells and whistles. But is it worth the cost of pulling in the vast overhead of "modern" frameworks, and their resulting complexity and maintenance problems, just to have those?