Please stop shoehorning everything into HTML/CSS/JS

The reason Debian eventually gained one is: internationalization. For languages that are written with a small alphabet (Latin, Cyrillic, Greek) it's fairly easy to set up a TUI in the console character grid, but for languages with lots of characters (notably Chinese/Japanese/Korean) or languages that rely on letter-shaping (Arabic), you really need a fully-featured graphics library to be able to draw legible text.

Making new users feel more at home ("this looks difficult, like a thing for hackers" vs. "this looks a bit like Windows/macOS, how hard can it be?") is a side benefit of offering a GUI installer, but quite an important one IMO: first impressions do matter.