I think Sega also seriously fucked up with the Saturn. There were lots of claims of it being more powerful than the PS1, but nobody could extract that power really. A Saturn dev at a studio I worked at had a complete breakdown just trying to keep up with what I was doing on the PS1. I feel they burned a lot of industry bridges with that machine.
I'd have loved to see the Dreamcast succeed because I'd always been a big fan of Sega, but I think a lot of things just went awry for them.
I heard the Saturn was originally designed as a 2d machine, sega saw what the PS1 was going to be capable of and bolted on 3d. Hence it was a mess. Is it true it could only use quads not triangles for polygons?
Yep, but obviously a quad could become a triangle with two shared vertices. I never worked on the machine myself, and my memory is definitely fuzzy on this, but I seem to remember one of the things stressing out my colleagues was the poor transfer rate of getting textures into the video hardware, and the space being quite limited. So, all textures ended up being down-res'd by 50%, which just made everything look terrible.
I'm sure there were other issues, that's just the one I can vaguely remember.