Honestly, if that example is from your game then I think you are falling into a very familiar pattern of self-sabotage by being too hard on yourself. To my eyes, your overall art style looks very coherent. So it looks good to me!
I can't tell you what to do, but I can tell you what I did and what happened as a result:
I spent 20 years on my first commercial indie game. I've always been poor because of a physical disability, so I had to "hire artists" or purchase assets all along the way. As a result, my game has a lot of mix-and-match art styles because my game world in particular was very niche and there just wasn't a lot out there.
I took the sales from my release and put them back into the game by purchasing a chunk of work from another indie artist. That fixed my world tiles and environment uniformity. I also did the same for my character graphics. But the monsters... This was harder.
So I downloaded a piece of indie software here on itch, an off-brand Photoshop of sorts. In it, there was an "AI Powered Filter" (this was local so I didn't realize until just recently, it wasn't even "AI" it was just machine learning calculations. But this let me make all my monster graphics look closer to the same style.)
I am an open and out-going person by nature, and so I was honest about this "AI filter" usage on this particular part of the game.
Sales stopped almost immediately, YouTube subs poured away, and I got hit with the "just hire an artist" while holding a $12,000 receipt for all the artists I hired over the past 10 years alone while living on 800 bucks a month.
Two weeks ago, I closed the doors of my tiny solo indie dev studio and now have about $1,800 in debt I still have to pay all the artists I didn't hire.
So whatever lessons you can glean from my own experience, I hope they serve you well.