In PHP ecosystem there is a tool called Rector. It helps a lot in automated refactoring. It helps a lot in updating from a bad design pattern to another, update code to match a given framework updates, etc.
Maybe we could create a similar tool for client side Javascript to migrate away from jQuery to vanilla Javascript. Websites youmightnotneedjquery.com have a good collections of vanilla JS alternatives to jQuery.
While one could do it manually, on larger code bases, it is extremely tedious.
Maybe such tool exists and I am unaware of it?
At first, I thought about having such transformation as an optimization step in the bundler, but this is unnecessarily redundant and might cause a lot of troubles.
Good for you. However many many people are still stuck with ugly ass slow poorly written jQuery code.