Story-wise, having the game be from the perspective of slimes, a common enemy type, is an interesting premise. Having them be otherwise friendly but misunderstood by humans has potential to be a compelling story of prejudice and empathy. It makes me wonder if there is a deeper lore reason for humans to mistrust the slimes.
Despite the good premise, I don't think the characterization and dialogue takes good advantage of this. Most characters feel interchangeable from one another because of their shared friendly tone to their banter. I noticed in your devlog that you want to later add accessories to make the slime characters more distinct. I think that's a good way to differentiate them design wise, but I would encourage figuring out what their unique personality traits are and have the dialogue reflect that. Their accessories could also reflect those personalities as well. Also, having NPCs with unique personalities would encourage me to want to interact with them and would further develop your world.
More of an idea than a critique but with if you made each party member different common enemy types? Instead of four slimes, you could, for example, have a party of a slime, a skeleton, a bat, and an orc. Something to think about and would easily make each party member stand out from each other. Just an idea to consider.
Having tutorials is good, but I feel the game tries to explain too much at once. It tries to cram too much information to the player and I find that I retained very little of it. I think it'd be better to introduce one or two mechanics at a time. I did gather that certain slimes have affinities, so certain items will work better being used by certain characters. It took me a few battles before I realized you had to drag and drop from the inventory to equip items. I think the tutorials probably mentioned it, but again, the information overload meant that got lost in the noise.
With that said, I will say that the UI during battle is very intuitive. I found that it didn't take me much effort to figure out how to use it. It was very second nature. Handling different menus and states can be complex but I didn't notice anything break during my playthrough and I managed to learn to navigate the battle system without much issue.
Is there a way to equip items to characters faster? Dragging and dropping items to each character one-by-one in between battles got tedious after a bit.
I think I did 8 or so battles before I lost interest. I never did reach a boss that another commenter mentioned. I eventually found the battles repetitive and the story hadn't progressed enough to keep me engaged.
Overall, I think your team has a solid story premise and a good grasp on designing a functional battle system. My suggestions would be on adjusting pacing, characters and dialogue, and rebalancing how tutorials are handled.