I desperately want to like this game. It reminds me of happier days spent playing a public domain game called Labyrinth on my Commodore 64... but far more frustrating and unfair.
My first gripe is that when I find a ladder, almost always a) there's a hole in front of it, or b) no hole but I fall down anyway. This seems remarkably unfair, especially b). Whether this is an artifact of your maze generator, or deliberate, I cannot say.
The second is that you seem to have wandering monsters that drag you down if they touch you - but you never see or hear them coming. I suspect this is related to my "falling through solid floor" issue. Far more excitement could be had in the sequel by adding cues to indicate a monster's proximity and where.
Thirdly: Gates. Some open. Some don't. There is no visual cue as to whether one will open or not; no visual cue as to how many keys you have to open said gates. From comments I gather that you have to collect these and then find an X to reach the exit for the secret ending.
Finally... I am convinced that your maze generator modifies the levels during the game! In my last game, I walked around the cell holding an exit ladder, started again and found a gate and hidden doorway that wasn't there before. I don't know about you, but I rather like maps that stay relatively static. Who needs monsters when the maze itself seems to be the monster?
If you make a sequel, I suggest:
1) 'freezing' the generator during gameplay;
2) adding indication of monsters in vicinity (forcing the player to run away);
3) making the keys more important - say, by placing them on lower levels and forcing players to drop down to collect them, then struggle to conserve same on the way up;
Actually, with relation to 1), another option might be to, at regular and distressing intervals, have the maze move things around - holes, gates and so on - in other words, play up the angle of 'the maze IS the monster'. In other words, go down to get up - preferably without falling too far and being eaten.
So technically, a good concept, but unpleasantly hard in the wrong way as executed.