People get bored of a dungeon for two reasons. The first is people now a days have the attention span of a gofer. Nothing we can do about that. Second thing is once you learn how to beat the puzzle it loses its appeal. That we can fix.
I propose making a labyrinth. Now that sounds really hard but hear me out. You make a dedicated layout of interconnection passages. Then you add doors at every junction point. What doors are open changes when ever the dungeon is empty of players and then a player enters. This would create a new path and new dead ends every time you go threw. (It wouldn’t change for each person so that people don’t get separated). Then you can spice it up by having different threats in each area. Could also have multiple big bosses with their own loot unique from each other. However you only encounter one of them per run threw.
This would make the replay value of the labyrinth extremely high if you wanted to collect all of the boss level loot.