Perspective from someone who lives here: both airports are needed and nothing to do with "pride". The DXB / AUH airports are 130km / 80miles apart. Thats 90 minutes with no traffic, and more with "normal" traffic. Both cities have large, high density, high income populations. Residents of both cities do not want to drive / bus 1 hour out to DWC for their flights in this case both cities residents add considerable travel time - much more so for Abu Dhabi the nation's Capitol.
Look at the example of DFW that was supposed to serve both cities, Dallasites did not want to shutter their former airport and it coexists nicely in that space. Similarly we see today Tokyo residents rejecting Narita with the resurgence of Haneda.
Talking some USA examples: San Diego and Los Angeles coexist, nobody is shutting down wither airport. Orlando and Tampa, Miami and Ft. Lauderdale, San Francisco Bay area, (SJC OAK SFO), New York area etc. Nobody wants to drive an hour or more to an airport when there's an existing one close by. So this fantasy of closing AUH and DXB in favor of Maktoum is just that.
It's an idea that looks good on paper to people who don't actually live there.
Not all your examples are good. Most of them have a much larger population than Dubai and Abu Dhabi combined. DFW maybe the closer you have.
Still, I see two important aspects to take into account.
I get the fact that those two cities can have airports catering there own need, this is not so surprising. But in reality, those airports are not there to cater to local demand, this is almost an added benefit. The purpose of this mega-constructions is to build hubs.
And this is what is surprising: the fact to want to build to major hubs so close to each other. This is the unique aspect of this place and the aspect that is playing more we ego and political considerations than with facts.
If I were to tell you that two cities, one with over three million people and the other with about half that, 130 km appart, were to have separate airports for local traffic, probably most people would say that it would be easier to have just one but more practical for each to have one. If I was then to tell you that each of this cities had to have a world-class hub, to would call me crazy. This is the problem here: we are talking about two different problems that may well not have the same solution.