As a designer, if you cannot make a bootstrap button not look like a common button, then I question your ability to use basic CSS. I’ve made a lot of websites look nothing like Boostrap, and as Bootstrap gets better I can do it with even less lines of code.

As a long time frontend designer/developer, gone are the days of writing CSS from scratch.

Contrary to your belief, looking at other people’s CSS is not usually a beautiful thing. And if you have a dozen developers, they come up with a dozen ways to name classes.

Using a framework like Bootstrap, minimizes those issues, and allows your team to scale up their efforts with a good enough baseline. You still need to learn how to manage CSS perhaps with BEM, and you need to reduce the amount of CSS you write, so using CSS Grid and Flexbox helps in that regard, but failing to take control of Bootstrap is a missed opportunity.