Hololive fan games are generally impressive to me. No matter what the game is, there's always someone talented behind the helm. And the passion the devs have can always be felt. And that sentiment very much applies here. Idol Showdown for what it is, is a pretty good game from a team of passionate devs.
In general the game is a pretty fun, easy to learn fighting game. I do feel like it could be just a tad tighter, but in general it feels perfectly fine. The art is pretty good. Music is good. And I really appreciate the Virtual Frontier mode as a Holo fan. I love recognizing all the jokes, and piecing together who the items belong to. My only major complaint is again, I think the game could just feel better than it does. And I also don't like how the arcade mode has no continue option. I don't see any reason why that can't be there. Not having it there makes the arcade mode less fun. I also think some more little touches could used such as victory animations, maybe some unique win art, pre battle interactions. But again those are just little touches. Asides from that good game from a small team. Though one I admit has limited appeal.