> The simple alternative is just around the corner: sprinkle vanilla JavaScript where it’s needed

Is it simple though? From my experience, apps written with "sprinkles" tend to become very complex very quickly. Unless the author means something else by "complexity".

I see a coming soon page one time that had a background image, a logo in the middle and 5 lines of text. That was the entire thing. Wondering why it took so long to load I view the source. 30 js files, 5 css, a hundred html tags with 10 classes each.

Wondering the same visiting a web shop I found a seemingly infinite amount of js. Digging a bit deeper I ended up getting lost in some enormous library for rendering unicode smiles with data uri's. It seemed like a good idea as each page was already making many hundreds of requests. If they add 100 smiles to a product description it probably never loads.

In my experience you can avoid things getting very complex by just refusing to add new "features". If that is out of your control it isn't your fault. Build them the pyramid!