Hi, undergrad here. That is to say, I’m not anything close to an expert in web design, but just in the course of making a simple static website to show recruiters I realized a lot of lessons like these about how modern HTML/CSS/JS can really handle anything you throw at it without having to worry about frameworks or precompilers. Sure, Bootstrap and SASS helped get a prototype up fast, but I feel like that gain in pr…
OTOH, css frameworks go the other way. The more you have to do, the more apparent that bootstrap etc. get in your way, largely because css isn't a "complete" language.
I know some few who swear by them, but the majority of people I know who did html/css exclusively for years feel they can write by hand anything they would want from bootstrap in less time than they would waste in fighting things like selector specificity and other inflexible choices.
YMMV of course, and you can pry postcss + preset-env + mixins from my cold, dead hands.