Sure, but that’s not an argument for not doing it either. As I’ve been trying to explain, I’ve had practical success building applications using the kind of software architecture I described.

I don’t like to get into personal backgrounds in these discussions, because as a rule I think arguments should stand on their own merit. However, just for some perspective, I wrote my first professional GUI around three decades ago. More to the immediate point, the longest I’ve maintained and extended a single GUI built using the architectural pattern I described was over a decade, and that one was probably more complicated in its requirements than a lot of web applications you’d see today. So although it’s just one anecdotal data point, I think it’s a good demonstration that this kind of architecture can work well over an extended period.

There're too many things which can go wrong with visuals. Incorrect order has smaller probability than a bug in a style somewhere which makes data invisible. For the 2nd reason you want to test that thing somehow else anyway: unit tests don't catch rendering bugs.

You seem to be making some implicit assumptions about the platform here with the reference to styling. In any case, this is why I mentioned that you might want a different testing strategy for the presentation rendering layer to the code that collects the presentation data.

Totally different. SVG renders vector 2D graphics, WebGL is a 3D GPU API. Try to render something slightly more complicated than rectangle of solid color, and you'll see.

Sorry, I’m not sure I understand the point you’re trying to make here. I was saying that web-based GUIs might have moved from rendering graphical content using one of the plugins a few years ago to rendering it using one of the native technologies today, without necessarily changing the content itself. Obviously which native technology you’d choose would depend on what kind of visuals you were creating and how you wanted any interactions with them to work.

Once you know the data, you do not want to run your code at 60 Hz (or 240Hz if you're really unlucky) computing functions of time and updating things. It's almost always a good idea to use the GUI framework for playing animations. They do better with rendering and power saving.

To the best of my knowledge, the GUI framework you are describing does not exist. You might be able to extract some basic movements that could be handed off to something running at a lower level with hardware acceleration, but ultimately you still need code to define the way the layout should animate according to whatever rules your system uses, for the same reason you need to define a static layout before or after the animation that way.

I’m not sure what you’re getting at with “doing better with rendering and power saving”. Can you clarify?