Wow, this is such a great little game. An excellent demonstration of why simplicity in game mechanics can be a boon as long as you nail the theme. The game is barely a game- player choice is so limited but it's so fun to watch I hardly notice. Game designers take note: graphics (animations are great, from charismatic bobbing of characters, dopamine explosions of gold, choice usage of lighting effects to highlight mechanics and enhance theme), music is well crafted (fits theme, beautiful but not distracting, mixes it up enough to never be annoying), just enough depth to be fun (I never learned about all of the classes, but there were enough differences that I had favorites and had an impression that I could study them more to dramatically improve my strategy), and the user interface is minimalist, but responsive and respects the player's time all while obeying the theme.
Should you try and improve upon it? Not really- you could take lessons learned and make a similar game, but this game definitely knows that it could overstay it's welcome at an hour of playtime, at most. Too much would need to change to support more levels, more player control, and the theme and fun would suffer IMO. Want more depth in mechanics? Play darkest dungeons. Want more length? Play the 1000s of idle games out there. Want both? Play the Idle Champions of the Forgotten Realms. Want 30 minutes of fun and nostalgia? Play this game!