I'm not so sure. Attractiveness is a good quality if you want a claim to power through networking, but it's not the only way.

Take Thatcher or Merkel. Both women for whom this arguably matters even more, not attractive, and not even coming from a background that lends itself naturally to climbing hierarchies. Kohl, Merkel's mentor used to often refer to her as his "Mädchen", ('girl', but diminutive, only used for children) and she basically back-stabbed him and took control of the entire party.

There's definitely ways for unattractive or more generally, people who nobody expects to rise to power to do exactly that.