The Queen Mother had no interest in power, and her way of thinking was quite different from the average male immortals.
She didn't see the point in exhausting herself to substitute for Hao Tian, only to deal with suspicion upon his return, breaking the previously harmonious family atmosphere—all for the fleeting benefit of enjoying a few days as the Heavenly Emperor. That wasn't a favorable trade-off.
Even if she wasn't the Heavenly Emperor, with her cultivation level, there were hardly any beings in the Primordial realm aside from the Six Saints who could make her bow. So why bother?
If she wasn't holding authority, then she would have to find a way to delegate it.
The first step was to gain recognition—she needed the approval of all immortals; otherwise, having them constantly blocking the gates of the Turquoise Pool would be quite troublesome.
As for competence? Look at Hao Tian, he's been the Heavenly Emperor for so long, and hasn't run into any real calamities, right?
