PRIDE was the top organization during the height of Fedor’s career, so I don’t see how never going to the UFC could be held against him. Over the course of 10 years he was undefeated, and was never really challenged. During that stretch he beat 5 former UFC champions, former PRIDE champions, elite grapplers, top K1 guys, and guys that were physically bigger than him. The type of run he had at Heavyweight is unheard of and will never be duplicated.
Like most fighters he’s stuck around too long, but that doesn’t diminish what he accomplished during his prime.