Well, if you need your CSS handled like you want for example. How about setting some plugins for PostCSS, configuring Sass (with parcel you do it using package.json), If you are building a large project you will need configs, sooner or later. How about aliases? I stop now ;-)
then you are configuring PostCSS and Sass, but parcel itself is zero config. I think Fusebox could learn a lot from the #0cjs trend, just like webpack did with v4