No, Jenova was what threatened the planet millenia ago, she is now active and the planet is in trouble. I think she is a bit more than a background bad guy.
The planet could have designed them with the capability of stopping Meteor. The planet is full of mako, lifestream, materia, knowledge, etc. I think it could match a small ball of the stuff.
Seeing as there's a giant crater at the top of the planet, it seems a bit obvious to me that Jenova didn't just fly. That plus the existence of the black materia, and the pictures in the Temple of the Ancients.
