First of all thank you for playing mine.
As proof of concept, this could work!
First impression, I think because it is still very early it is very overwhelming in terms if the UI. Too much information given for a new player to take on. Gradual onboarding of mechanic and dungeon could be better designed in MVP.
On design for RPG wise, the RPG mechanic itself is well defined. I think you based this on DnD like stats system. I have no issue on that.
For improving this past prototype, the presentation you go any way you like. The current one is tactic based combat, I supposed because it gives better sense of turns and visual. If you going for that style maybe you can try reference Wakfu for the movement style + visual style.
Exploration could be added, you can also go any route with this, but the simplest probably be Darkest Dungeon.
You probably need a lobby system too, menu based for me would be less enticing for player. Some sort of abstration such as the lobby is an explorable tavern or a town would be exciting for player to mingle and explore. Upgrade can also be tied to shops in the town so that player has basic purpose to explore. Maybe become an adventurer life sims with player housing. This is for longevity of the game itself, because there must be other activity other than dungeon crawling for player to spend time and invest into, if not the case atleast a way for player to spend their dungeon crawling loot.