It would be amazing having sci-fi mega cities, perhaps connected via underground railroads and between them just nature undisturbed. It feels like we are so close from a technological standpoint to make that happen.

I wholeheartedly agree. And I believe we have everything needed to make that happen - but if everyone has good living conditions, that just isn’t profitable / exploitable for the corporate world. Happy people means it’s harder / impossible to scare them or make them angry at some perceived threat / enemy, and exploit their dividedness. All megacorporations without exception and a lot of mid- to large size businesses thrive on exploiting workers who are too divided to unite and demand a fair share of work and profits and acceptable working conditions.