It might be a minority view, but I loved Jonas Quinn’s character! Why? Because he made Teal’c a fully fledged [/edit] character. The both of them interacted so well. Teal’c was part of the main cast since episode one, but he never felt like a real person with their own emotions until season 6.
Christopher Judge is an incredible actor, but until Corin Nemec came along he wasn’t allowed to be a whole person with their own agenda. Even small stuff, like not sharing his ice cream in “Prometheus” / “Unnatural Selection”, would have been unthinkable before Jonas came along.
I think, retrospectively, telling Jonas to fuck off be with his people when Daniel came back hurt the series in the long run. Corin was a good actor, and Jonas was a good character.
Shanks leaving and returning had a complicated impact on the show. AFAIK, he wanted better opportunities to act - and they just would not give him any. So he got to exit with exactly the kind of complex episode he asked for. The showrunners evidently took this to heart, and started making the show more like want he expected, y’know, after he left.
In comes the same-purpose-different-character replacement, whom contemporary audiences rankled against for not being Daniel. But yeah: Jonas is distinct, well-written, and well-acted. He gets some really fun bits in some solid episodes. (I always think of the diner scene in Nightwalkers.) He would’ve easily been a beloved replacement… if he’d had one more season. Maybe if Shanks had seen better success outside of Stargate. But just about none of the actors in any of these series had stellar careers outside the franchise. It’s like Jason Momoa snuck off with a bag full of everybody’s prospects.
So Daniel comes back, and it’s a whole thing, and suddenly he’s getting episodes like Lifeboat. He gets to flex, in every sense of the word. Not just him, either; Judge wrote The Changeling himself, in the middle of season six. The show ultimately benefited from Shanks calling the studio’s bluff and leaving. He even got to come back and enjoy the benefits. But wow did Corin Nemac get screwed in that exchange.