I played a little of your game (~30 mins or so) and it was good fun.
I think the strengths of this game are the world building and the interesting characters. You did a decent job on those and don't worry about using the rtp, I always find that it holds up well if used creatively and you made some interesting maps with it.
I was impressed with how smooth the cutscenes played out. I sometimes struggle with this myself so it's good to see it done well.
As you pointed out yourself, I think the main issue is the balancing, although tbf I did get lost in a cave I wasn't supposed to and my levels skyrocketed in there I was gaining a level every two fights or so LOL but good times anyway.