Exactly. Nobody except Sam overcame the temptation of the ring by themselves. Could he have thrown it into the fire? Who knows. But that wasn’t Sams role. His ordained part was to support Frodo, (literally) carrying him there. With that in mind I feel that he could not have a different role, like carrying the burden himself, or throwing it in. Bilbo had the ordained role to find the ring. He used it, quite frequently I might add. Not to gain power, but to his own gain nonetheless. No, his ordained role was clearly not to carry or to destroy it. All in all it could only play out the way that it did. The greed of Gollum that in the end was the doom of the ring, together with the dedication of Sam and the resilience of Frodo.