I think one of the biggest issues is that 'regular' content is very easy outright for many players with a decent amount of experience with the game. Many encounters are very generous in regards to not punishing players for their mistakes and a lot of players have access to gear that increases their damage and health to a point where they easily survive most things that the game throws their way. I've seen people soak up multiple AoE's and survive due to an attentive healer - and it isn't unusual for a dungeon to involve pulling multiple enemies at once and then killing them with AoE.

I'd like to see more engaging content that takes a similar approach to the higher floors in POTD. You need to be cautious with how many enemies you pull at once, there's traps to watch out for and every enemy has at least one special ability to watch out for. At the very highest floors getting hit by any AoE at all will result in death. So the stakes are high and the rewards are actually pretty decent all things considered. Unfortunately actually getting there is needlessly tedious - you need to first find three other people to team up with who will be around at set times. You also need to tackle 50-100 without a single wipe which isn't too difficult in itself and most people wanting to do the higher floors will have already done already dozens of times over. One of the biggest challenges is finding people with a schedule that aligns with one's own. A lot of players in this game are very flaky in that regard.