Was it legal and politically palatable to build there, or in the neglected neighborhoods around it? In the USA, unless you're talking about actual greenfield land, rail-supporting development is usually illegal to build.

The reason rail works beautifully in other countries is that you can get off the train and walk to useful destinations, even if where you disembarked isn't where you live. Shinkansen in Japan have tons of shopping, nice restaurants, and hotels all within a block or two of the station. So there's a reason for non-residents to stop as well as residents. And because everything surrounds the station there's no point for residents to go anywhere else.

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.

That would be ridiculous, if it would up to 1 hour round trip it maybe would be more effective.

The other line (running from downtown to the airport) was also a total of 1 hour 30ish minutes including bus from my house to the terminal, then rail down to the airport. It otherwise was a 30ish minute drive, tops, and driving is what almost everyone chose to do if they had the car to do so.