This is a common, or at least not uncommon, concern of Fantasy readers trying to decide whether or not to dive into the Jordan's masterwork. Long series, even fourteen volume ones, faze inveterate Fantasy readers less than books with a slow pacing, so I will now address that concern more deeply.
In short, while The Wheel of a Time is hardly a fast-paced series, everything matters. No matter how small the event or character may be, the odds are strong that it/they will in some manner be relevant to the future. The butterfly effect is real here, as characters you might forget, or believed to be localized to a subplot long finished, will likely turn up again far from where you last saw them. People may compare it to GRRM's A Song of Ice and Fire, arguing that GRRM's literary bloodbath is far more fast-paced, but this is an illusion. How many subplots in Ice and Fire truly matter? How many gripping intrigues developed by the High Lords playing their Game of Thrones actually ended up shaking Westeros and making a real difference to the story? The answer is very few, yet the story seems fast-paced due to GRRM's immense skill in the art of storytelling. He creates a near flawless illusion of speed that keeps the reader hooked. Which is no small feat considering that GRRM's grimdark tale has no natural endpoint. (Yes, I am aware that the Others must needs be defeated, of the prophecy of Azor Ahai and the prince/princess that was promised, and of course that someone must finally sit the Iron Throne uncontested. But the Others and the prophesy are marginalized by ruthless High Lords playing their game of thrones, and who sits the Iron Throne one year may be dead along with all their kin the next. Hardly natural endpoints for an epic Fantasy of such scale, in my mind.)