@Vee I'm very happy you are still doing these, especially as they have little details I'd long forgotten (like Rusty returning).
I grow to loathe Mack around season 9 and that never fully goes away, but he was very important to allowing both Karen and Knots to grow into a more confident place at this point, and the show really needed his energy. He and Michele clicked instantly and Knots wisely did not do what a lot of shows did and set him up as a heavy antagonist before telling us to like him.
Regarding your thoughts on Richard and the community, especially Karen, I think where Richard benefited is that he was easy to understand. A go-getter who went bust, someone to pity, someone to take under their wing. Karen liked that because it made her feel good and she could help someone who needed help and would be clearly appreciative of that help. Laura was more complicated, much more guarded, and complexity is something a lot of people do not have time for. Laura tends to be "othered" for much of her time on the show, drawn more toward other damaged people than the designated heroines, which is one of the more realistic elements of Knots for me, and why I think the show loses a lot of its soul without her.