The loot tags in the chest in the OldWatchtower structure point to a non-existent loot pool called "dungeonChest" resulting in the chest being empty when genned in game. I presume this is meant to be the "minecraft:chests/simple_dungeon" tag instead and that it just got missed when updating to the vanilla loot tables systems.

As it is such a simple fix, here is a dropbox link for a fixed version of the structure with the correct loot tags in place: https://www.dropbox.com/s/0teqco3us79uhre/OldWatchtower.rcst?dl=0