Siptah definitely needs some End Game loops and goals. Farming ??? to get T4 Thralls so you can make armor and weapons with Eldarium to farm more ??? is a little limited. Need a loop to jump onto with your gear.
Most obvious one is epic dungeon in tower like Wine Cellar or Warmaker. Or a portal to “New Lands” there that allow you to go in, get the loot and come back.
Purge mechanic. The tower should belch open up portals in the safe areas that belch out Elder Things to attack player bases.
Survivor settlements with Valeria giving out quests all around the main island. Go bring me this or that, kill this or that (including players for PvP) you could get imaginative and not just do fed ex and rat killing but that is a start.
Conquer Elder Thing fortresses inside the Maelsrtrom Area. There should be fortst there teaming with Elder Things. Think Mordor in Lord of the Rings. You should be able to raid them and free prisoners to claim them as thralls.