I do think that's somewhat true in software, but I think games are more of a mix of art and software, and in art it's much less common to find consistent winners outside of the mediocre category--- Thomas Kinkade makes consistent nice-looking paintings, but Picasso produced a lot of crap amidst his masterpieces. I'm not sure it's possible to take risks on game design and not end up with a reasonable number of duds, even if you're solid and professional on implementation.

It is true that most game-industry positions aren't really for designers, but these days a large number do involve some amount of design, especially if you want the game to be unique in some way. For example, AI programmers are in an odd position of doing "just implementation", but implementing a system that deeply impacts what kind of gameplay and design is possible (in some cases they quite literally write the tools that the designers will use to do things like write NPC behavior).