From a pax perspective, yes the A220 is great. From an airline perspective, there are regrets. The reliability is poor and it is exacerbated by significant quality problems in manufacturing and part shortages. Maybe these will get fixed in the future, but I’ve heard it has scared UA away from the plane and pushed DL to look at used aircraft to offset slower fleet growth and lower utilization.

Bottom line, at the end of the day the airlines will focus on planes that make the most money by being reliable. These are rarely the newest and most passenger friendly airplanes.