Hi Yoder, I use vanilla SCSS with a super simple Gulp file.
IMO as a teacher and developer, sticking to the core language means that every hour of study is taking your much deeper into your learning path.
Core languages allow you to write clean, tight, reusable code that specifically addresses the project at hand, whereas Bootstrap it is a generic solution - resulting in code which is most often bloated and ugly, with extra markup and hundreds of lines of unused css / js - see @labiej - uncss.
Bootstrap tries to solve every problem in the world - bootstrap.min.css is currently 187 KB!! It’s like hiring a crane to move a stick. That’s insane, and site performance is paying the price.