Well... this was quite a fun game to play. I really enjoy playing those games with this cartoon-ish art style that are usually quite addictive and have much variety in their artstyle ^_^
I liked the different stages, enemies and bosses. Made each transition from one stage to another feel more interesting. The legendary items were cool too, kept them from the beginning till the very end. I also liked the abilities that you got with the sometimes, my fav one from the warrior was that boomerang-star, from the hunter the bear trap and the flying dragon from the monk dished out enormous damage as well.
One common issue with games like these: grind and repetitive gameplay. The fact that you've played passively in this game made it feel a bit easier, but it was also somewhat boring at first. Thankfully fights get a bit tougher in the middle part of the game ( at the end you are just too OP xxD ) and then strategy is somewhat needed.
To make the game more interesting in the longrun I'd just suggest making 8 stages per "area" with a boss at the end without having to go through all stages twice. I'd also suggest having more ways to obtain different and more unique items, my only ones were by getting legendaries from those chests, buying some in the shops and once getting them from that wheel of fortune. I'd also be kinda cool if you could have a different combination for your party, like, idk, more slots for characters and different classes too, that'd atleast cover the passive gameplay aspect up a bit.
Oh, well, this was a long review, but I just hope I could express everything I've had in my mind very clearly in this one ^_^ Hope you'll take a look at this and consider some of those things for future games that'll be somewhat similar to this one ;)