> pre 2000
I'm pretty sure a lot of good technology is written pre-2000. Why you'd want to throw it away is beyond me. Just because something is old doesn't mean it's outdated.
> difficult to experiment or fundamentally change
Generally with mature products this is true, so the solution is to use an immature product? Why not just take the time to learn the existing products so that you can experiment or make your changes.
> security and performance are hard
It's always been that way, and it always will be. I doubt a new library/platform will change that. The only thing it will do is make the developer an expert on the system (since she designed it).
The diagrams don't make sense, and seem to miss the point. Not all scripts will cause the layout to change. Some may, but the renderer shouldn't be controlling the script, except in extreme or very specific cases.