The empirical evidence weighs in favor of the more modern MMA training style, and Rickson himself is not active in high level MMA (fighting or coaching) anymore, so constantly criticizing the technique of MMA fighters today rubs many people the wrong way.
Well, most MMA fighters ARE bad strikers or grapplers. Guys with a striking background suck at grappling because they have learned it just enough to try to defend themselves and vice-versa. Now there are truly well rounded fighters in MMA but they are the absolute minority. But there are also fighters that are not only bad strikers but also bad grapplers and are still fighting in the UFC.