This adaptation is... really boring.
Now, I'm one of the few people who actually played the mobile game before the adaptation came out. And yes, I know that the story in-game isn't interesting to begin with. But they could've at least done something to make it more... bearable...
Let me start with the story. Like I said, it's bearable. It's as rpg as you can get. You got a young knight destined to save the world and... well, that's it. There are some things that one might think would make the show interesting (I'm not gonna show that here cuz it's a spoiler), but even that made it super boring. Did I mention there's so much exposition? Cuz there's a lot.
The characters aren't that better. They're as cardboard-cut as they get. Dense hero who just goes with the flow and no proper motivation? Check. Beautiful sidekick that acts as nothing but eye candy? Check. Emo kid out for revenge? Check.
And I think this is the problem with mobile game anime adaptations. It takes away the imagination of what it would be like to be the protagonist of the story. At its core, mobile games like king's raid have protagonists that serve as stand-ins for the player. And you can't really do the same thing with anime.
Everything else is pretty mediocre: Art, sound, setting, etc. Overall, this is not a great adaptation. I'd rather watch a show that twists its original plot rather than do nothing with it. But hey, that's just me.