As a reminder of how much we've fallen, look at the appearance settings for Windows 95:
http://toastytech.com/guis/win95schemes.png
You can change the colours, fonts, and sizes of all the UI elements, and have everything looking exactly the way you want, down to the pixel size and RGB value! That was possible 25 years ago, with the technology and computing power of the time, as well as developer effort.
For fun, I decided to open the linked site in IE6 with its default theme, and compare how its UI looks. In almost exactly the same vertical space taken by "Firefox Compact Current" which shows two lines of tabs (with cut-off titles), an address bar (with cut-off URLs), and navigation buttons, IE6 manages to fit four lines: [1] A full titlebar, [2] A menubar, [3] Navigation buttons, and [4] A full URL.
With current Firefox, you only get three choices: "large", "huge", and "WTF"; and Mozilla plans to remove the already-too-large choice to make it two. No doubt sometime in the future it will become one, if this trend continues.
What's more, the UI of IE will change size, font, and colour if I change them in the system's settings, so I can have the same consistent appearance throughout. If I want a huge UI, more interesting fonts, dark mode, or whatever else, I don't have to set it per-application, unless it's an application like Firefox which draws its own UI...
What happened? When an entity like Mozilla would rather spend a lot of effort on complicated site-facing features, yet remove already-trivial yet extremely useful configurations like these, it's really hard to not see that software is going backwards and becoming more user-hostile.