One thing that really sours me in esm is that this is possible (fictional main.js):

    import Vue from 'vue'
    import jQuery from 'jquery'
    global.jQuery = jQuery // to get the next line to 
    work
    import Bootstrap from 'bootstrap'
    import 'bootstrap/dist/css/bootstrap.css'

Then my head explodes. Why would importing a .css file from my JavaScript ever be a thing supported by any tooling. What is that line trying to communicate? What does it even mean to my current scope? (hint: nothing)

import became a giant "do something cool on this line" that maybe the tooling you're using knows how to translate via (say) a webpack loader.

For anyone wondering, that line gets translated to the browser dynamically including css on the page.