The division into separate levels was interesting. Allowing player-directed risk-reward for pursuing new farming grounds when an upcoming level difficulty is uncertain.
Goodness me those gauntlet levels can be punishing when you're not over-leveled. Grinding earlier levels is the way.. although it feels tedious when leveling up various skills still isn't enough to pass a target level.
I have some small suggestions that might assist with player feelings of progression despite the powers and values being exactly the same: some additional visual marker in the guild window that represents improvement due to all the upgrades a player has done (it appears that you gain more people when you clear more levels), additionally in the background music perhaps a character represents a particular instrument and when that character levels up the quality of sound produced by that instrument gets clearer in sound quality with more nuanced patterns that add some variety to the score? (I love the chill vibe of what you have already. I'm not recommending changing your creative vision -- just subtle nudges the aesthetic you've already got. There are plenty of little layering tricks. But yes... a listener can identify higher quality sampling rate.)
Thank you for sharing your wonderful work with us! It's clearly apparent much care and love went into it. Wishing you the best with your full release!