The concept of “legitimacy” is kind of ridiculous. Without genuine political independence there is no such thing as democratic legitimacy; no matter how many elections you have.
If your government is actually the servant of unelected multinationals and investors, what does it matter if you elect them or you don’t?
if you want legitimacy you need to liberate your government from the domination of private capital. Otherwise all you have will be parties competing with each other to serve business, not the population.