Not really, at all actually. Jirachi may be a great special wall, sweeper, and revenge killer, but I can't just slap it on any of times like you could with Genesect. Jirachi is often times a Pokemon that patches up holes in a lot of teams, or otherwise known as the "glue" that holds a team together. Still, that doesn't mean that I can put Jirachi on all of my teams. You might as well say that Landorus-T should be S-rank as well, since he can function as a great offensive pivot, wall, revenge killer, and sweeper. But do you see people using him on every team? Of course not. Once again, you kind of contradicted yourself. Sure, Jirachi may be versatile, but that doesn't make it S-rank. If a Pokemon is versatile, then that means it can fulfill a lot of roles effectively, so by saying that versatility alone wont make it S-rank then saying "However the fact that jirachi can fullfill nearly any role your team wants AND be good at each of them (unlike mew for example) is what makes it S worthy", is a complete contradiction to your argument, since you're trying to prove how versatility does NOT make it S-rank. You just restated versatility, not proved it wrong.
If being able to fulfill numerous roles effectively makes a Pokemon S-rank, then Landorus-T, Garchomp, Celebi, Rotom-W, Tyranitar, Scizor, and Latias/Latios should all be S-rank, since all of these Mons are very versatile and can function effectively in many different roles.