I mean, there are so many particularities in each place, it's just too simplistic to discard them. What does the existing infrastructure look like and how can we use it best? How expensive would it be to install a different system, where does the money come from, and what else can the city not afford for that?

Another interesting case would be Kyoto, which relies mostly on buses although there are some train routes. But when they built their subways, there were a lot of construction delays because workers found ancient objects, had to call some archaeologists etc. So the city gave up after only 2 lines. Above-ground trains are also relatively rare although they exist. But you would have the same issue, existing buildings and cultural heritage.

It's just a complex issue. Both can be totally viable solutions, depending on context and implementation. My point is that it's kind of dumb to start raging against buses now as we have different issues.