Wow! That is a sweeping generalisation if ever I heard it! I can't talk for RapidWeaver, Sandvox or Freeway, but Flux 3 is actually a very good tool.
I downloaded the trial version of it and was impressed, so decided to purcahse it when it was on special offer, so got it for half price.
Flux 3 has import facilities, which none of the others do and you can start with a blank template and it shows you all your html and css and you can create both Inline and External styles and it shows you how websites should be created, so you have to work with the layers, so the body layer and navigation, footer etc. It gives you a good working idea of how websites are created and you can see the code view too.
It takes more getting used to than the others, especially if you have no knowledge of html and css, but if you work through the Quick Start Guide that is available with it and all the online tutorials, then you should have no problem and you can create websites that are also html 5 compatible.
From my point of view Flux 3 is by far the best of the lot - you just need to take the time to learn it.