This looked interesting and I tried it for a while and here's my thoughts.
Map:
You definitely need a map or a representation of the area that you are at.
It doesn't need to be fancy, it can just be Squares joined together by lines.
Just like what Corruption of Champions 2 and Lilith's Throne did. for their maps.
As for the game environment itself. each layer of the depths can be designed to be quite different from each other.
Each of them can have their own danger, that the player character has to overcome somehow.
Combat:
It needs some work, which is not surprising given that the game is new.
You can take inspiration from DoL (Degrees of Lewdity) as well with their combat ending either you win by defeating the enemy, or making them cum and you lose by being beaten up until you cannot continue combat.
You might want to think about a combat system if you want to have ranged weapons or some magic involved.
If you plan to have ranged weapons when maybe combat system that includes distance might be needed, and if there's distance, then speed comes into play.
Leveling system:
Given the inspiration from Made In Abyss, your character will need a lot of skills to be able to survive in the lower depths.
A poor rookie will just perish in the harsh environment.
It seems like there is some sort of leveling system from what I see, you can level up Running in this game.
You can use it to work with the distance system that I mentioned above, get enough distance between you and the enemy and you can then escape the battle. Maybe even have different proficiency at navigating different terrain, so your character can get better at moving in forest area or swampy area or rocky areas, something to think about.
It would be interesting if your character has some sort of scouting skill or stealth skill to be able to spot and avoid dangers, if spotted, be able to run away.
Of course this scouting skill can be helpful for finding Relics or navigating through dangerous terrain.
And since you are inspired from DoL, you can take inspiration from it as well, like the leveling system.
It's harsh in DoL if you have low skills but it becomes easier to manage things when your skills go up, so why not have it in this as well?
It makes a lot of sense to have many skills related to exploring and diving into the depths.
Art:
The AI art as placeholder right now is fine, I suppose.
You can look into Lust Doll Plus for what the Dev did with their paper doll system, to see what might work with your system.
As the game is super early in development, I guess we will have to wait as the game is being worked on.
One piece of advice, break the game development into smaller manageable chunks and don't be afraid to simplify things.
Like if developing a particular part of the game is hard, you can simplify it for now and move on to other parts of the game.
Degrees of Lewdity wasn't made at one go after all.
You can always go back and rework a particular system as you get better at game development.