All this ones are good for Responsive Design... they are good for the ones who don't need to spend a lot of time in creating a responsive mobile friendly design...
Like every other wysiwyg and "site building tool" before them -- utter and complete rubbish. Developer ineptitude and scam artist bull at it's finest. They are incapable of producing semantic markup, what they vomit up and have the giant set of brass to call markup is so shamefully bad it makes Frontpage from twenty years ago look good, and on the whole if you "need" something like that just to build a responsive layout, you probably shouldn't be building websites! Developers are dumber for idiocy like those even EXISTING! They are SEVERAL grades worse than CSS frameworks on the stupidity scale -- which given those are idiotic mouth-breathing dumbass BS? Not a fan.