The structure Ancient City is still not generated under already existing chunks (which were created with 1.17 and earlier).

I have a 1.17 world with a diameter of 12,000 blocks. When I optimise this world with 1.19 pre 1 and start it, the Ancient City structure is only generated outside my existing chunks.

EDIT:

 
I tried it with another world (radius 2000 blocks). The structure is not generated there either.

You can download the world here (Expires after 30 days and I can upload again if necessary):
https://ufile.io/nanmjoks