I notice that there are a lot of knife people that seem to forget that knives are made to cut. No folder with a 1/4" thick blade is going to cut worth a crap.
Overly thick bladed folders are all show and no go.
I don't own many fixed blades, but I do own a Marble's ideal of 1/4" stock. It's convex ground and 1 1/4" wide, and cuts very well. Why is a 1/4" folder any more ridiculous than a 1/4" fixed blade?
My Ideal is no crazier than a Mora and a thick folder isn't more so than an Opinel. You simply aren't going to use a thick folder the way you would a thin one. Just because you or I don't have a need for a thick folder does not make its existence ridiculous.