[Earendilyon]

the phantom:

I think that Gandalf was "unfitted for the required task" (that task being the defeat of Sauron).

According to Letter #156, Tolkien didn't think Gandalf was't fir for the job, but that the task had become too grave for the Istari to cope with, within the rules set for them:

Gandalf alone fully passes the tests, on a moral plane anyway (he makes mistakes of judgement). For in his condition it was for him a sacrifice to perish on the Bridge in defence of his companions, less perhaps than for a mortal Man or Hobbit, since he had a far greater inner power than they; but also more, since it was a humbling and abnegation of himself in conformity to 'the Rules': for all he could know at that moment he was the only person who could direct the resistance to Sauron successfully, and all his mission was vain. He was handing over to the Authority that ordained the Rules, and giving up personal hope of success.
That I should say is what the Authority wished, as a set-off to Saruman. The 'wizards', as such, had failed; or if you like: the crisis had become too grave and needed an enhancement of power. So Gandalf sacrificed himself, was accepted, and enhanced, and returned. 'Yes, that was the name. I was Gandalf.'

And I would add that the destruction of the Ring was not possible, making the good guys losers no matter what.

I agree with you, that it was not in the power of the 'good guys' to destroy the Ring, but not that that fact makes them "losers", not in the sense which is mostly attached to that word. They would loose for all the knew, but were not losers.