Right, I guess these frameworks target ease of use and performance, probably styling is the last thing in the priority list.
Python is the same everywhere, so is HTML, even the widgets (components) from one framework to another are similarly named; but, when it comes to customization, it seems that some web development frameworks use one styling framework and some other something else...and the abbrevaitions to refer to classes vary; for example, way behind the scenes, Nicegui uses Tailwind CSS....and Shiny, Bootstrap? So, yes, having to learn the styling framework adds a whole 'nother dimension.
The thing is that I first heard about pure-python web development framework as "dashboarding" frameworks; so my expectations and desires were for a rather compact interface where one can have many inputs and outputs, radio buttons, checkboxes, dials, result widgets, some small plot...but the various frameworks I have been looking show things way too spaced out!
I tried the <div> tag, but that did not change the inner widget at all. In particular, I am talking about the ui.input_select component, and the vertical distance between the label and the dropdown...the height of the sub-widget for the selection is too tall...I would like to make it smaller, as in the docs.
Here is a comparison between
What I see in the docs, ex: "Choose a state:"

and what I am getting:

Any hints?