If download size is at all an issue, jQuery is the first thing to go. I have a tiny collection of helper functions that make 'plain js' almost as simple as jQuery in most cases. Almost.
For example, at the very least I'll have a '$' helper function that makes document.querySelector(All) simpler/quicker to use, and I use a helper function for events to make it a bit more like $(<selector>).on().
But considering the fact that I have quite a few projects where the client will upload some huge image for the home slideshow or where there's no time or incentive to do any lazy loading of images, jQuery is often still the pragmatic solution. Especially when other devs need to deal with the project at a later stage.
Besides, 400k of (blocking) JavaScript can be the difference between the site loading quickly on mobile and the user giving up.