Nibbana isn't the ultimate equanimity, it’s the ultimate happiness. The word for happiness, here, sukha, can also mean bliss, pleasure, ease.
"We don’t start out by being equanimous about everything. All too often, people read about the Buddha’s teachings and they see that many of his teachings end in equanimity. The factors for awakening end in equanimity. The four brahma-viharas end in equanimity. It sounds like that’s where we’re going. And many people say, as long as that’s where we’re going, why don’t we just go there first? Why bother with all the steps? Well, the Buddha’s equanimity is very different from ours. The Buddha has found a true happiness. Notice that he doesn’t say nibbana is the ultimate equanimity. It’s the ultimate happiness: the word for happiness, here, sukha, can also mean bliss, pleasure, ease. And it’s worth our while to aim at that ultimate happiness, that we put forth an effort to attain it. Equanimity meant is for the things that either would pull us from the path, or prevent us from moving further along on the path. You have to develop equanimity for those things, the things ...