But the point of the comment is that both Bootstrap and Tailwind are facilitators when you don't know/want/care about getting your hands dirty with CSS. Tailwind happens to be a little less abstract than Bootstrap, but still you're not fiddling with "low level" CSS.
That abstraction is what brings the "sameness" factor in play, though.
You absolutely have to know how CSS layout works to do anything even marginally complicated with Tailwind. It's not a replacement for building flexbox layouts or dealing with Z-indexes or knowing how to compose elements for different viewport sizes. All it's actually separating you from is (most of) the "Cascading" part and having your styles separate from you elements.
I haven't used it in ages, but it used to be that Bootstrap also shipped drop-in CSS that would give you decent-looking styles on all the common elements, so a single minified style sheet would give you that classic "2010s startup" look.
https://news.ycombinator.com/item?id=11287413
(The underlying webpage is no longer around. But the HN discussion is.)