Absolutely. The only thing Open Gaming has to its credit is that it was used by Dungeons and Dragons. If Dungeons and Dragons had not used it, it would never have meant anything, and now that Dungeons and Dragons does not use it, it does not mean anything.
(Yes, I'm sure you'll want to inform me that a few other insignificant games have, for whatever reason, fallen under the Open Gaming banner. I don't care, and neither should you, about those other games. By the admission of the second-largest company in the industry - the only other company in the industry that has market share worth talking about - D&D is fantasy roleplaying.)