Why do we need great political leaders? Where are they leading us and why should we follow those who have an appetite for so much power? People should think for themselves and follow their own convictions and espouse true virtue, not get carried away with the mythology and worship of politicians. Great political leaders are like super heroes in movies and comics: they're a cheap, vicarious substitute for being a leader (or hero) in your own life.
Why do we need political leaders at all? Why do we need a mediocre (wo)man on top instead of some kind of direct democracy?
If you've got leaders at least be sure you have good ones.
WRT power: you're so wrong. Great political leader is capable of creating a country. Or rethinking one. They produce power out of the thin air, for everybody to use. Mediocre leaders? They tend to "consume" power. Exactly what you are fearing.