I agree with the points about it being just a large set of declarations, there aren't a lot of good ways to lazy load CSS (that I know of) so in some cases you're pushing a lot of bytes that you don't need to and creating dead weight.
Also the presentation in markup point is one I have been saying for years. We hear about the death of tables and why it needed to happen and go back and do similar stuff. But without extensive use of something like jQuery you have to do it.
I think these frameworks are awesome for people like me. I'm a backend coder, and I am not that good at CSS. I love being able to whip out a layout and interfaces in a fraction of the time, so I can focus on what I do best. It's not that I'm afraid of CSS (I can write it) it's just that I'm afraid of wasting time.
This is the primary reason these frameworks have flourished IMO. Useless? Not even close.