I did UI development for quite a while too, and in my experience having very specific layouts (and look) in HTML is easier than in frameworks I used (Gtk, Qt, UIKit...).

Main difference is that HTML has affordances to size elements "upwards" whereas in other toolkits you need to do this manually (e.g.: estimating text size is a thing, in html you don't need to care about this)

Now, this also encourages original layouts which are untrue to platforms which is not a good thing imo.

You also don't need to estimating text size in QML, XAML, Forms, VCL, and when you need it is hardly any different than dealing with CSS fonts.