Unpopular opinion but I feel like deep dungeons were always badly designed and players have just accepted it because they're straightforward, mildly fun and were "new" on release.

The save system is extremely restrictive and unnecessary, makes playing with different friends or FC a pain and going back to the start after a wipe on a high floor is punishing in a way that doesn't feel good because it means you have to chew through all the easy floors just to get back to the engaging part. The leveling floors are so easy they put you to sleep and become boring very fast.

There's a good base idea that's spoiled by clinging to restrictive systems and gimmicks.