Hisar replaces 8-12 villagers on food with a reasonable amount of research done, and can be very useful to help mitigate population lost due to scholars. Prior to the imperial age research nerf it could offset almost all the population scholars made up in your mosques. Since they want us to make more scholars now it should probably be buffed a bit if that is the role they wanted it to play. It is also not a dead landmark if you are pop capped.
I like palace too, but it’s pick rate is definitely inflated by one of the more popular build orders bugging out Hisar (honed blades/MAA)