[quicklime]

I think the author probably agrees with you that London won't "fall" in the sense that it will cease to exist, or even fail to prosper. Rather, she's arguing that London is the most important city in the world due to its connectedness to Europe, and as a result of Brexit it will fall behind other cities and lose its position as the most alpha-est world city that there is.

Not catastrophic by any means, but if someone is living in London because they consider it to be the center of the world, then it's a big deal.

[muninn_]

Perhaps, but as you said it's not catastrophic.

Even so, you don't need to be the center of the world.

[quicklime]

Sure, but sometimes people are sad when they lose things, even if they don't "need" them.

I totally agree that the title is clickbaity, but the sentiment expressed in the article is legitimate.