That's a strawman. I don't need 1000s of lines of JS to swap a UI. I can do it in 1 line with Web Components: oldElement.replaceWith(newElement). And those modules can be lazy loaded like anything else.
This is just DX in name of UX, which is almost never a good idea.
And maybe you're fine with throwing a server computation for every single UI change, but I'm not made of money and I much rather have stuff on a CDN.