then I got it -- the ability to use code generation to be declarative is incredible.
having the ability to mix declarative (HTML / data structures) and imperative (javascript) is what makes react so powerful. The ability to do that almost-natively inside the language is amazing.
Rebol & Red are examples of this, there's a GUI dialect called VID [1][2] and in companion with this is a Draw dialect [3][4].
1. http://rebol.com/docs/easy-vid.html
2. https://doc.red-lang.org/en/vid.html
This approach lets you blur the lines between MVC responsibilities. If you wanted to create a widget that had some traditionally 'business-logic' role (like network sync or database interaction) you could do that. I'm not recommending that but there's value in flexibility.
The FB/google share buttons on websites totally break MVC. It's just a button but it has cookie & network traffic.
I hate those buttons, people often argue they 'break the web' because of weird privacy/performance side effects, but developers use them because it's convenient to 'drop in' the platform integrations.
By comparison -- integrating an android app with GMS requires modifying a bunch of files (xml layouts, java source, multiple build dependency files). You can't just 'drop it in'.