Just completed floor 50 the first time. I halfway liked it. I had the most fun with a group that was trying to go as fast as possible, avoiding monsters when they could but getting all the chests. I also like the rare super strong NPCs that can show up. Some of the traps can make for interesting situations. I also like how it almost feels like a full adventure.
The problem is that's all there is to it. On top of that, it was designed for a group of level 17s with no class composition requirements. WHY does every new piece of content have to be made for someone who hasn't played the game or hasn't played in months? Level 17s and newbies have enough stuff to do. These players haven't learned any dungeon or game mechanics so you end up with content that requires no knowledge of game mechanics. That's bad and boring. Additionally, this place negates your gear - just another sign that there's no point in gearing up or picking your stats in this game.
How to fix it:
STEAL FROM GOOD GAMES. Add random events and objectives to floors. Here's some suggestions I thought of in 5 minutes:
Oh no, a Tonberry is chasing you (this one is from your good game, ARR around 2.0) so you have to move quickly through this floor.
A mysterious merchant has appeared who will let you trade 2 pomanders (stop it loc team) for one.
Certain monsters on a floor have had their stats turned way up. They have a black aura.
Cultists are summoning a boss on this floor. Get to them and kill them before they succeed.
You found a magic lamp with a genie inside who will grant you a wish. Choose wisely (+weapon, +armor, +exp, +gil, or a massive buff for the next floor)
This floor has no map and is shrouded in darkness. Stick together and make your way to the exit.
This floor's exit is behind a caved in wall. You need to lure bombs to the wall to destroy it.
A treasure goblin appeared. Where have I seen this one before?
There are 4 switches that you need to stand on at the same time. Split up and go do it.
A miniboss appeared. Kill it.
The second thing is to GO NUTS WITH ITEMS. You don't get this stuff outside of deep dungeon, so use this place to test new stats and effects. You opened a silver chest. +1 weapon level and BONUS!!! your weaponskills sometimes go off twice. Your spells sometimes cost no MP. You have a fireball proc. XXXX weaponskill is AOE. Whatever. The haste floors are fun. Do more stuff like that.
Finally, make it harder. Level 60s should be able to handle some basic dungeon requirements. For starters, all of the telegraphed moves in there right now should be instant. Next, a healer should be required at the bare minimum. A tank should be present. Monsters should actually hit decently hard and it should encourage you to pay attention to your surroundings and what you're fighting. A cyclops should be dealt with differently than a morbol, etc. Also these bosses are seriously a joke for the amount of pomander stuff we have available.
Stop designing stuff for four level 17 lancers to go in and win because it makes it extremely boring for anyone who has been playing the game for more than a month.