15 Tifa was able to pick it up due to sheer adrenaline brought on by rage and willpower. Using it was a different story.

There are many reasons Cloud would not use the imitation Masamune Blade. The first being that it's too weak to benefit anyone... like the Excalipoor.
Also, why in papa smurf would Cloud want to use the same weapon as his ultimate enemy? That would be a total mind smurf and Cloud's messed up as it is.

Also, in case it was confused at any point, there is no equality between the Masamune and the Murasame or Yoshiyuki. Both the Mura and the Yoshi are shorter than the Masamune by at least half.

BTW, I've previously mentioned the oddness of hero Cloud wielding a sword which some legends say is one of massacre while villain Sephiroth wields the holy sword Masamune (though it was depicted as an evil sword in Chrono).