[sjsamson]

>One of the lines is from downtown to an airport

You don’t provide enough specifics about your local situation, but it’s been long noted that airport rail lines underperform. The author Alon Levy’s blog and others in the transit space have covered this. TLDR: They fail serve the local riders well, in an attempt to serve less frequent airport riders who are more likely to pay for a taxi/rideshare, rent a car, get picked up/dropped off, etc. There are often poor airport connections, like people movers or airport connectors, getting to the right terminals, etc which creates more friction and confusion.

>neglected neighborhoods that never got the rush of development and gentrification rail was supposed to bring

Rail and transportation infrastructure generally is an enabler for re/development and land use, but not a guarantee of it. Necessary but not sufficient by itself.