I couldn't disagree any more, at least in my specific field, where my data is generally static and extremely relational. Writing JS to do what SQL does is... a pain. But having SQL on both the frontend and backend would dramatically simplify the translation abstractions between the two - for a similar reason that node on the backend simplifies translation abstractions. It ultimately means less code and less thinking.

How else would you suggest full applications run in the browser. Desktop apps make use of SQLite all the time even when they are mostly server backed.

An example is that Telegram maintains a local db which stores the most recently accessed content so you can scroll through past messages and media without having to request them every time you view them.