I will blame Eberflus for many things, but LB play isn't one.
Murray has always been the guy you see. He put up five years of tape like this - as a full time starter! - before he ever got to Dallas. Year 6 looks just like all the others. I truly do not know how an LB that bad continues to get that many snaps from 3 different teams, and my only guess is that it's his first round pedigree. If he was a 6th rounder playing like this, he'd be in the CFL by now.
Sanborn is just athletically limited, and having a terrible defense around him really exposes that.
Shemar James is a 5th round rookie, who weighed in in the 3rd percentile for LBs per Mockdraftable. Not gonna be your run defense savior, and that should have never been the expectation.
Liufau is the only one I am actually curious about, because he's had good moments and he's had bad moments, but he's just been doghoused for some absolute trash 'backers. He is the guy I would want to be giving reps to in a lost season.
Anyway, coaching can only go so far. I think that James is the only talent on the roster that's coachable, because he's a dude who just straight-up needs a year in the practice facility. He needs to put on weight, and he needs to see plays a beat faster, which are both common for a 21yo rookie. If he can react a little faster and hold up a little better, then I think he's got the movement and aggression to become a successful pursuit LB.
I don't know what Liufau's deal is (he needs coaching on tackling, that's for sure), and Sanborn and Murray just are what they are.