I like bulma, but it doesn't quite cover the full feature set of Bootstrap (and that's not bad in itself, it's a matter of what you want to use in what case).
Technically with normalize.css + lostgrid you're good to go in most front-end projects.
Where I find bootstrap useful (and to some extent semantic ui) is rapidly prototyping backend admin applications and offering a nice baseline for other developers to do semi front-end work in a documented way.
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