Also spacing/padding increases to much that then at some point you only have like 1 word per line, and the screen is half blank space

Everyone jumped on the only-use-rem train when mobile started dominating because it provides relative units that scale better rather than absolute pixels.

In practice it doesn't really mean much outside of blog-like text so when doing layouts it's more of just a standard everyone agrees on using everywhere because it's easier to stick to one for consistencies sake and it does the job. I don't think many frontend devs ever test zooming text using a browser anyway, their main concern is variations in screen sizes, basically device variation not manually zooming text. But I get the arguments to limit it to text.

Incompetence, and thus obedience to a mistakenly-generalised caricature of "good practice", is my guess. I used to use em everywhere for exactly this reason. (The only reason I didn't shift to "rem everywhere", "flexbox everywhere", "web fonts everywhere", etc. was obedience to some different caricature of "good practice".)

I've never seen a CSS framework that's good. (Unless you count https://simplecss.org/, but that's of very narrow usefulness.) They're all made by the kinds of people who don't understand web technologies, and seek to hide them behind a layer of abstraction so they don't have to think about them any more. Unfortunately for them, there's a reason the web's how it is. Some of it's backwards-compatibility, but most of it is that a large group of very clever people failed to find a way to make it any simpler without breaking something important; and so, the framework people tend to break important things.

If you find yourself reaching for something like Tailwind or Bootstrap, just use inline style attributes. It's easier for everyone involved.

On the contrary, I've always found HN's font size to be one of the worst parts about the UI. I actually have a userstyle set to override it

  body {
      font-size: larger;
  }
  
  .comment, .default, .comhead {
      font-size: 14px;
  }
  
  .subtext, .pagetop {
      font-size: 13px;
  }
  
  .title {
      font-size: 16px;
  }

It's not the prettiest CSS or the most well done, but it works and it's better than the defaults imo.

I disagree, I field a lot of reasonable adjustment requests and a staggering number of people don't know about basic functionality. They are also not interested in them.