NYC has a lot of money, but this is a huge project, involving continuous disruption to a system that must continue carrying 6 million people per day throughout its completion. The NYC subway has more stations than any other metro system on earth, with 424 stations, of which 133 are already accessible. Hitting 95% by 2055 means around 10/year on average for the next 29 years. While it could always be better, for a system that is over 120 years old, this seems not too terrible to me.

Also, not every subway station is equal. Some see significantly higher ridership than others, or are more critical transfer points, and so can be prioritized to have more impact sooner. It seems like that is what they’re doing.