It only opened a couple of days ago, so there's that, but I think you can expect it to remain in similar condition, notwithstanding wear-and tear for some considerable time. Graffiti is rare on the London underground, and is generally removed quickly.

I believe London also has a significantly lower number of homeless people, although comparable statistics are hard to find.

This is "Crossrail", aka the Elizabeth Line, the Tube's major new extension that opened this week (after years of delays.) So it hasn't had much chance to get dirty yet.

Beggars and homeless people are common in London, but less common on the Tube since you can't get very far inside most stations without a ticket.

You ever been in Courthouse Station? It looks beautiful compared to the rest of the system.

That said, I dont think of the T as particular grungy with graffiti its mostly just poorly maintained.