Whilst not disagreeing with what you are saying, it is a bit like saying Newton shouldn't really be given so much credit for his work on gravity and the laws of motion as there were plenty of other people around at that time who would (and did) have arrived at the same theories. My point was that Marius did those things, not that he was the only one able to do them, and as a conseqence we had Sulla, Caesar, Augustus, the Roman Empire and the current shape of western civilisation. We may well have ended up in a similar situation had he not existed but he did and despite his role in shaping the future he is not well known.