Art captures the Hollow Knight atmosphere for sure.
Now the gameplay feels floaty, jumps don't carry much weight you need to increase the gravity, slope walking could do some work (I struggled with this in Unity) you need to make a script to push the player towards the slope when he's on one so you eliminate bounciness. The Knight from Hollow Knight seems impossible to defeat, I don't have any options of countering his attacks so to hit him I need to take damage. You should also consider adding white flash on enemies you damage them, there needs to be some kind of an indicator.
Would be a ton better if there was sound and music.
I think you're missing a collider in one spot.
Now you could make improvements to this game but this isn't your IP, I would recommend you to make your own IP with this mechanic of plaguing a civilisation and making it fall where you are the villain in that story.
So basically this game but re-skin the NPCs and the player's character.
This is if you plan to finish and release them, of course it's totally OK to just make a Hollow Knight fan game, it's up to you.