It's a similar feeling to the one I had while in China and riding its extensive and convenient high-speed train system: How does the the US not have metro systems with the technology, cleanliness, and efficiency of a country that only started running a metro a decade ago?
Most of the metro systems in the US, from SEPTA in Philadelphia to the BART in San Francisco to the subway in New York City, feel decrepit and crumbling when you ride them. The only automated systems in the US are either airport trains or small "people-mover" systems in places like Miami, Jacksonville, and Morgantown, West Virginia.
As a New Yorker, the subway is the system I am most familiar with. I have a deep, love-hate relationship with it. It takes me everywhere I want to go at any time of day, but, at the same time, it's clearly living on borrowed time. There are delays and malfunctions constantly and many of the cars look like they haven't been updated since the 1980s.
It seems crazy to me that New York, possibly the wealthiest city in the world, is still using signal equipment dating to the Great Depression, while Dubai operates a completely automated system. Obviously, switching subway to a driverless system would be a gargantuan effort, but the process has to be started at some point, right?
At the end of the day, the Dubai metro is a brand new and relatively small metro system for a budding city. But, after riding it for a week, I'm convinced that it shows that top-notch metro systems can be run by any city that makes it a priority.