It is.
Because London is so big and so ever-changing, the reputation and fortunes of each district cycle.
I grew up in Wandsworth in the seventies. It was pretty down-at-heel. All the big Victorian houses around the Common were originally built for newly-rich tradespeople and their families who needed to be within reach of the centre, but who wanted to live where there were trees and open spaces. By the mid-twentieth century, that was the inner city. You couldn't give away a huge Victorian house at that time. No one wanted red brick and stained glass porches and tiled fireplaces and coving and sculleries. The houses were split into flats for the less-prosperous.
So the reputation of the neighbourhood dropped, and the area became undesirable. Which meant that property got cheaper. Which meant that by the end of the century, aspirational young people could afford to buy there. Which meant there was more money about and hip restaurants started to open, and junk shops became antique emporia. There was a shop on Wandsworth Common which, when I was a kid, had a dusty window and some kind of bakelite machine on display. I never knew what their business was and I never saw anyone in there. Before I was thirty, Marcus Wotsisname had turned it into a fashionable expensive restaurant. Wandsworth is very wealthy now. Same goes for Greenwich, Peckham, Clapham, Balham.
And usage changes too. When the docks became defunct, Southwark and Bermondsey - which had always been rough and lively - became rough and deadly. You really wouldn't want to be caught on Tooley Street after dark in the seventies. Especially if you had blue hair and red boots. For instance.
Now, Tooley Street is bustling, alive, touristy, reborn.
Many people will moan that it has lost its working-class character - and it has. But that character was lost when the docks closed. It wasn't redevelopment that killed it.
London's always done this. The West End - let's say from Regent's Park to Trafalgar Square - was a huge urban renewal project. And to make it happen, acres and acres of slums were cleared. The character of the place was not just changed. It was expunged, mercilessly. Thousands of people were summarily chucked out.
But you rarely hear people moaning that Regent Street has destroyed the soul of London. No one ever suggests that Portland Place was much more chummy before it was gentrified.
Is London in decline? Undoubtedly bits of it are. And bits of it are on the up. That's how London survives. Two thousand years, and counting.