I'm always skeptical to such big-infra projects for a reason: they are not flexible. We design something today that will be ready after more than a decade on sc

I'm always skeptical to such big-infra projects for a reason: they are not flexible. We design something today that will be ready after more than a decade on scale hoping to have correctly projected future needs. Surely trains are very efficient and commercial-only on-rail transports for non perishable/non urgent goods can ALSO run on renewable when there is enough energy also stabilizing the grid and leaving perhaps a side channel for perishable/urgent goods, a thing no other practical means can do BUT they are still not flexible. We design a network hoping that in a decade and for more decades it will be useful to pay it back. That's why I'm for air and water transports: a plane/chopper/drone a ship/sub/* can go anywhere on air/water, we all needs infra on departure and arrivals places. They cost more in operational terms, but they are flexible and cost far less in infra terms. Development of "flying cars/taxis" and "new cheap ships" seems to prove that such line of thoughts have various advocates. Surely that scale only in a distributed and not that densely populated world, are we heading to a mass genocide perhaps?