Its pretty clear that Mark and Micheal Reeves don’t focus as much on design and iteration so much as the ideas behind their creations. The content formula for their videos is different from the other youtube creators you mentioned. If that style of video isn’t your cup of tea, thats ok.
As for the inventions themselves, I have to disagree. I think some of Mark’s creations are fairly well designed, such as the later versions of the glitter bombs.