I'm not the only one who thinks Ancient Cities are currently too difficult to find in Survival, right? Well, here's my rudimentary solution to the problem: Explorer Maps, often found in Stronghold Library chests and more rarely in Stronghold Corridor Altar chests and Woodland Mansion chests. I think that's a pretty reasonable difficulty for obtaining them.

If it's possible, in the future I may make them a rare trade from Cartographer Villagers.