Looking back season 6 was the last season where ER believed that beloved characters deserved nice things. Like Mark's dad's storyline was an example -- Mark made peace with his dad, his dad got to live out his life in a way that made him happy, we all cried and everything was good even though Mark's dad died. Carol got the feel good ending with Doug too.
After that the writers just stopped believing that TV audiences wanted to see good things happen to their favorite characters. Nothing good happened to Carter, Mark (duh), Peter, Luka, Kerry, Abby, Sam, Rocket Romano, etc. To this day I don't get why the writers wanted so many calamities to pile on top of each other. Why did Romano have to face The Attack of the Helicopter ... twice?
The only nice thing was the final season had more of the optimism that was a hallmark of the early ER seasons. The finale had some optimistic threads. Rachel Greene was going to be a doctor at county. Peter and Lizzy seemed to want to start things again. Carol and Doug were doing well.