Seems like this show's M.O. is to have two and a half episodes of plodding dialog, followed by half an episode of action that is more dramatic tension by weight than cool fights/set pieces.
I don't hate this show, I just kinda wish it was better planned out. (Edit: in the meta sense. The actual planning that must have gone into this show itself is really impressive.) I wish this show came first instead of Rogue One, and that it wasn't called Andor. Knowing the Rogue One M.O., it's not surprising that almost everyone died in the heist. And also knowing that a show is titled after a character, and is also a prequel to something else means there's almost no dramatic tension either because he'll have invincible plot armor the whole way. Which depending on the type of show isn't a terrible thing, but in a more grounded show like Andor where it's relying on dramatic tension more than anything else, and the harrowing feeling of vulnerability since he's just a regular dude and not a space-wizard, it very much undercuts things for me at least. I think if the show followed a character that wasn't Andor but still did most of the same things it would be a much more compelling experience.
I thought the tribal ritual was beyond weird.
I disagree with this. First off, I don't think there's any moment in the show where it tries to make you think Cassian is about to die (which is often the fake-tension trap that prequels fall into that you're talking about.) The show is not about "What happens to Cassian Andor"? It's about "What happens to Cassian Andor that makes him the person we meet in Rogue One". In that way, knowing the outcome helps set up the dramatic tension: we know where Cassian starts and where he ends up, and the show is about the journey from A to B.
That said, I think your proposal that the show would be just as interesting if it weren't a prequel is probably true. But knowing the main character won't die throughout it doesn't really weaken it.