I would beg to differ. The -500 could probably be deployed on 90%+ of AC's frequencies in North America. The outliers can be served by the MAX and 321XLR.

At the end of the day it will come down to whether Airbus can produce and sell the thing for a price that is competitive with the MAX and A320 after taking into account superior operating economics. The challenge for them will be that it currently costs more to manufacture the 220 than the 320 and they have limited 220 capacity, so the -500 only makes sense if Airbus can use it as a strategy to free up room on the line to sell more A321's.