A horrid defense isn't something that is easily corrected. It's a sign of laziness, of disinterest, of many other things, none of them good. You'd rather a scrappy, tough team that is overpowered by talent than a team that has no idea what coverage is. Bad habits instilled.
I'm still a bit baffled at how awful it is. Maybe some neophyte coach or a run-and-gun Doug Moe thing. Supposedly Langford, Poeltl, Jones, and Sochan are at least decent defenders, but it doesn't show. Keldon is a terrible defender and that's not enough to be this bad. McDermott's not even the problem.