Hourly rider count is the only thing that determines the speed of the attraction's wait, and that's what Frozen desperately needs.
But broadly speaking, THRC alone does not a high-capacity attraction make. Though you usually see a correlation, there are exceptions. The amount of people an attraction can hold at any given time is a virtue of capacity that I think is under-appreciated. For an extreme example, if FEA were a fifteen second long ride dispatching boats at fifteen second intervals and running two boats at a time, you'd double the theoretical hourly rider count but also cut the amount of guests it can hold to about a fifth.
Now for a real-world example. Kilimanjaro Safaris is a high capacity attraction with a modest hourly rider count. With a theoretical 1400 riders per hour, it's not one of the fastest loading attractions. However, the ride is 22 minutes long, and therefore can hold nearly 520 guests at any given time. Compare this to POTC at the Magic Kingdom which has a THRC of 3200 but with an 8:30 duration holds 450 guests at any given time in the best conditions. Kilimanjaro Safaris, while loading not even half as fast as POTC, holds more guests. However many guests are not riding one attraction at a given time are guests that are not otherwise taking up space in the paths or in line for an attraction. High THRC is good for the ride, but high overall capacity of a ride is good for the park. There's more to capacity than THRC.
End tangent. But as I said, yes, Frozen Ever After only desperately needs higher THRC to cut down that massive wait.