[2021] So... what would you have the AI do?

Basically, the current AI gives each zombie complete knowledge of all the blocks in the area. It's one thing for a zombie to know that a flagstone block is easier to destroy than a concrete block.
https://steamcommunity.com/sharedfiles/filedetails/?id=1797567696

It's another thing for a zombie to 'look' at a solid wall in front of them, and know that the wall is double thick in some places but only single thick in other places, and target the thinnest part of the wall.
https://steamcommunity.com/sharedfiles/filedetails/?id=1797567476

In this way, zombies don't really have a sense of sight. They can 'see' the player when not concealed, but everything else is navigating the world independent of what they could or couldn't see from their vantage point. It would be nice if that wasn't the case, but as always, A* pathfinding is just more efficient than other things out there, so changes along these lines could impact performance.

Originally posted by ⚜ JOST AMMAN ⚜: Thanks @Crater.

IMO faatal could save performance by reducing the area each zombie can be aware of.

So, for example, suppose zombies now "feel" the block strength in a 100x100 area around them... the pathfinding would need to find the path that far.

But if you reduce the area to (e.g.) 50x50 and apply the changes we suggested, maybe we could have enough processing power to make it work without tanking the game.

Now, if you reduce the area you can have other types of problems, like (e.g.) zombies never being able to find you on a Blood Moon. In that case my suggestion would be to use a very straghtforward, "light" pathing algorithm when the zombie is approaching from afar and only change to the other (new) pathing algorithm when the zombie gets near enough to you.

You're looking at it from the wrong perspective. Zombie's don't each have an individual pathing map- There is one overarching pathing map generated based on your surroundings from which every zombie derives it's path. It's part of why the current pathing method is among the most efficient of the available options.

Giving every zombie it's own pathing map even with a shortened range would dramatically increase the resources required to calculate, essentially multiplying the cost by two per zombie in the area- And it constantly gets updated as the zombie moves around, magnifying things even more. The way it currently is depends upon the movements of a single actor instead of multiple; That single actor being you.