The mouth of Sauron has spoken

[The Architect Of Fate]

so instead of being there, so that their powers cannot be put to good use lest it be seen, why don’t they just hide where men and elves can’t see them, and send anonymous and seemingly fortuitous, thunders, lightning and tornadoes to get rid of the orcs.

The problem with sword and sorcery fantasy is sorcery would rather tend to make sword superfluous, just as if the power to destroy a planet is insignificant next to the power of the force, then why does the Masters of the Darkside keep building more death stars to be blown up?

Their mission was to unite the Free Peoples to deal with Sauron, not to overthrow him themselves.

Boru

Indeed, the wizards were advisors, not warriors. They weren't meant to solve all Arda's problems but to teach the mortal races how to do that themselves. Trying to mold the world to their liking is what corrupted Morgoth and Sauron.