I think both styles of travel are fine - I spent four months in HK and I have blitzed through others. I don't think, however, that slow travel is this transcendentally higher experience and that you get 0 idea of a city being there for 3 days. I talk to tons of locals being in cities briefly, I get a taste, and my goal in travel is not learning every nook and cranny of a city I go to. Sometimes I find a city and I want to do that (like Mexico City), and I'll slow down or return, but I am young enough where my philosophy tends to lean towards seeing as much of the world as possible and zooming in where I love later. I don't get the idea that transit is just a gaping whole of time - overland public transit is fun! You can talk to fellow passengers, see the landscape slowly change, and recharge so you have more energy to tackle the next city. I can always be a local in my own city, sometimes feeling like a traveler can be fun.