True you cant blame a bike for being a rubbish rider but thats not what this threads about. In any situation that relies on design there are subjects of the design process that just dont work.
Much lauded though some rigid bikes are they have failings but some bikes have nothing but failings, what rigid bikes fit this category.
I had a made in Germany mtb once, make unknown, that now would have been judged a BSO but as it was early 90's I reckon it was just a poor interpretation of the brief they'd received. Angles were extremely slack, bottom bracket was very high, gearing was way too high and stem too long and low. Felt like it was designed for a hunchback and had zero poise at all, flopped into corners and handled like a fish on stilts