Personally I find The Orville practically unwatchable, regardless of how much stunt casting they do. The scripts are like something even Voyager would have thrown out, utterly generic, really dull and obvious comedy, lazy rehashed sci-fi ideas really poorly implemented and rarely thought through, with zero cleverness or originality, and all the depth of a petrie dish, performed by a cast of cliches desperately in search of acting talent. I don't think I've ever seen a more hollow, try hard, wannabe of a sci-fi show. It's like Trek made by people who are clearly fans of real Star Trek from back in the day, but don't understand how and why those shows worked, and aren't smart or talented enough to replicate it on a quality level in terms of story or character, so they spit out this cruddy fan-fic mediocrity instead. And yet, like an idiot I keep watching, hoping it will get better, but it never does.
Hate to come off like a hater, and people are of course free to like whatever they like, but I'll honestly never understand the praise some folks give this show. Still, to each their own.