Earlier quoted context omitted.
I love how tables "went away", and were widely replaced with bootstrap. Which gives you ... tables. in divs. But only 12 columns wide.
I think the value of Bootstrap was consistency across browsers. The grid system was the most important part. With standard Grid, Bootstrap is effectively legacy - you shouldn't really be using it at this point.
Bootstrap first adopted Flexbox for its grid system Bootstrap 4 (2018), and Bootstrap 5 (2021) added support for Grid. It's conservative about supporting new web standards, but I wouldn't personally think of it as a "legacy" framework.