Good guys of LOTR clueless?

[Rimbaud]

Quite, and I think Sauce has been striking proverbial nails on their teeny-tiny heads: Sauron was quite right. Excepting the chap with brightly-coloured boots, who doesn't really fit in with the rest anyway, nobody was capable of destroying the Ring. Nobody, deliberately, ever did so.

Further to Gandalf's quote regarding Sauron's belief in the Ring's destruction: it is clear that Sauron was sore wounded by the Ring-finger-smiting incident, and when he repaired for a good long time to the dark recesses of the world, must have believed that his injury was resultant upon the Ring's destruction, not merely the severing of himself from it. As has been ably described above, the realisation that this was not the case would have distinctly changed his outlook, and confirmed his prior belief that none could willingly destroy it afresh.