However, almost all of my experience with any Javascript framework describing itself as "modern" is a white page with no content of {{ placeholder }}a everywhere text should be.
Several comments on the RFC already seem to state the intention to slowly change Wikimedia into a more "interactive" experience. What I fear is that a framework such as Vue will make it _too_ easy to make everything flashy and modern and suddenly you end up with another SPA where a website should be.
The RFC talks about this shortly and mentions server side rendering but not much about what should be rendered server side and what shouldn't. The overview of problems seems more like a lack of structure than a need for a heavy JS library.
I am very cautious of anyone claiming they need JS for a web page. Applications such as the editors and turning into javascript programs is not something I worry about, but several annoyances new Wikipedia features have already brought me (especially on mobile) make me cautious of any suggestion to add even more javascript.