I think you're overstating how impactful railway land usage is, in total amount it's definitely a lot but per suburb or area it's not much and it more or less sits next to the rest of the suburb rather than dominating it. It provides far more value than an airport in my opinion. I can walk out my door and 5 minutes on to a train then into the city, there's no way to get a plane from my house to the city.

What you really want to reclaim I feel is roads from cars, we devote insane amounts of land to cars, car parking, and car travel..

The city of Adelaide is an interesting example if you're interested, it's a young city and built an airport 4km from the CBD, which means the CBD can't have tall buildings, the airport has a curfew, noise is a constant hot topic, and it takes up more land than our CBD and most prized suburbs do. It's likely sitting on hundreds of millions worth of real estate, while the train station takes up less than a city block and then the rails weave their way through the rest of suburbia. The most recent Southern Interchange, a car highway interchange, takes up more land than the train station does including it's convergence and junction yard, and all it does is connect two roads together.

The city also tore up all it's rail network when cars took over, and now it can't afford to put the rail back in now that it's proven to be the more sustainable and pragmatic option.