Q1: Pretty engaging, I don't think it needs a mechanical any other mechanical objective, maybe some petty narrative goal like chasing after a stolen drink so it feels like you're progressing towards something.
Q2: Audio was fine, music is generic action but that isn't a bad thing.
Q3: Combat feels alright, animation and enemy ai feel really solid. Hit boxes are a bit frustrating 2.5 D is a weird balance because I found it difficult I might suggest emphasizing shadows a bit more so you can tell if you and the goblin are on the same plane when you're punching or simply making the hit box more generous.
Q4: I think the one addition the game really needs is some aspect of variety. Perhaps little combos depending on mouse clicks to add a bit of visual flare and break up the monotonous pacing. It's mechanically sound but it feels very one note as to what you are doing throughout the game. Adding some variety to the combat would be nice.
Q5: It feels gently skewed towards too difficult. This only came up during the room fight against waves. If I was struggling to finish the wave and more enemies showed up before I finished the ones already there, it felt like there was no way to recover. A recovery mechanic such as healing from meter or heart drops from enemies may help.
Q6: Animation is adorable and lively, the backdrops look fine, a bit of extra character might be good, goblin TNT in the basement or some indication of what the building upstairs is supposed to be would be nice. Something that makes the spaces feel lived in I guess. Q7: No issues with performance but I have a higher end computer so that may not be the average experience.