Yes, agree. Problem is that the game is much faster now and being able to make quick decisions is required by every defensemen. Same with lateral agility. Some systems can "hide" those defects to some extent, but it's becoming harder and harder. Canes are probably on the more extreme side of things so I do agree that a guy like Edmundson would struggle more in that system, I was only commenting that he also had some struggles in STL as well, so it's not just Carolina's system.
Right; he definitely has a lot areas where he's solid. He's most effective when you have some predefined roles and tactics for various scenarios, like when opposition is in configuration A, do things 1->2->3, and when they are in configuration B do 4->5->6, and nothing that involves very quick stops/starts and agile turning. His ideal partner is probably someone that's a free-wheeling PMD with high hockey IQ; they can make up for each other's shortcomings.
If you limit your expectations, you will like what you get with him. He does a lot of things well, mostly things that don't require creativity, but nothing where you would say he excels at. Tamper your expectations, and he's a solid 4-5 D given the right type of partner. Otherwise, you would be sorely disappointed.