The UI is too cluttered and unclear. I've tried to play, and did win (I think), but am still not sure I fully know what I'm doing.
I got "endgame" text showing up at the top, while the enemy was still on screen. I'm not sure when it happened. Maybe it was when the enemy should have shown "hurt", though I'm pretty sure it was after that, maybe when they were lower health, as that is when I noticed it. The enemy did not show "hurt", so I had thought they just kept healing when I should have damaged them enough to hit 0 HP.
When a unit is at the bottom right of the board you can't see the button to use their ability. The 2 missing tiles in the game board feels out of place, and I was not sure what they were meant to be. It might help if they were black, or had some other indication that they might be a hole.
The cards feel too big and dominate the screen compared to the game board. I know it can be hard to make the text readable at low resolution, but with everything else feeling cluttered, I think reducing these to give more to the game board would help.
I think the almost "L" shaped tanish colored symbols might be the character's reactions, but I'm not certain, and they are really hard to see with so much else of similar colors. I actually stopped playing and just tried things to boost reactions to try to figure out if there was some indication of reactions since I had not noticed if there was any while playing normally.
In general, I think the colors need more differentiation. The background could change to perhaps be grassy greens. Maybe make the reaction indicators blue. The polearm targeting area could also use being a different color than the threat shapes. Just add a bit more color, as right now everything just appears a little too close and can blur together, rather than being clear at a glance. I know you mentioned planing to add a tutorial, and that will help with some of the issues in figuring things out, but even knowing what to look for the colors are too similar. I'm not colorblind, but someone who is would probably not be able to play this.
I don't mean to be overly negative. The game does have potential and could be fun. It's just that the UI made it really unpleasant to figure out and play. After playing through and winning I do have a better understanding and have some idea of what I'm doing, but I feel like I'm probably still missing a lot, and have to really look at everything closely to be sure of what I saw.