Cruise ships certainly used to moore up in the Greenwich stretch of the river at the and a few years ago there was quite a lot of coverage of the issue around it. Cruise ships require a lot of power while docked, and unless they connect to the grid they used to create a lot of air quality issues.
If there are a lot less docking then that's great, but there do still seem to be a number that dock there https://blackheathandbeyond.wordpress.com/2024/03/27/fairly-...
I know there was a push to develop a big new cruise port in the Greenwich stretch which was strongly opposed by locals for that reason.