What has being a homogeneous society to do with building a proper public transport system? Maybe you could argue that having only "John Johnssons" makes being nice to each other easier, but it's not a necessary condition for making a decent schedule or building trains.
Besides, Berlin has probably the least homogeneous population of all of Germany.
> On the other hand, we invented jazz and stuck a flag on the moon, so we've got that going for us - which is nice.
Resting on one's past laurels won't help solving today's problems. How well did that work out for the Roman Empire? Case in point: The US actually lost its ability to send a person to space, and hasn't been able to send people to the Moon for 44 years now.