Much like The Rebirth of Kingdom Lo, Resurrection Island is pretty much what it looks like it is - a lewd knockoff of Undertale that's even more furry than the original. Again, the designs and some of the art are cute, but there's fewer jokes with the things on the maps you can interact with. The translation is better, but there's less writing, so it's about even in terms of comprehensibility.
The ero scenes are still a little laughable, and the bullet-dodging segments are quite easy, but it was a pretty amusing way to spend an hour or two. It's about 30-45 minutes long, though you may need to do two playthroughs if you don't qualify for the true ending on your first run.

Lightly recommended, though I still wish the dev would either have better ero scenes (better animation and sound maybe?) or more story/gameplay in a future game. Probably better ero scenes.

I played this most of a decade ago, back in 2016, and was like "I guess I'll come back to it when the dev finishes it."

Well... that didn't happen. On the other hand, it was a pretty fun game, so if you already own it, it's probably worth playing through for a few hours. The inspiration from Risk of Rain is clear, but I think ultimately Risk of Rain is the better game, especially since that one was actually finished, so if you don't own Cavern Kings, you should probably just play that one instead.

Recommended, but mostly in the sense that if you already own it you should give it a spin, it's not as blatantly unfinished as many permanently-unfinished EA titles or anything.