Why Barron makes me nervous

This is not isolated, though this one is pretty bad, Now, this big run in not ALL on Barron, but he should have been in hole to make tackle. But he got reached and smothered...He has skills in coverage, but he lacks the ability to get off blockers. When he runs free, he does sometimes make plays, but this is not what a good run defense needs. A LBer who gets wired to blockers