Yes Bootstrap is pretty much the top favourite (across the various versions).
I saw an article recently (where I can’t recall) that it’s used, in some form or another, in 60-80% of all websites.
Yes, it has many classes (helper classes) but that aids consistency across large sites and dev teams.
If there is a trend it’s away from Frameworks since flexbox (which is rolled in BS4) and CSS-Grid are really gaining support both with users and developers.
I have no doubt that BS5 will be CSS-Grid based though….probably with fallback support for Flexbox since they are closely aligned.