Karras is mediocre to be honest, I know alot of people get beat by Myles Garret but I also seen him get pushed back numerous times. Our best linemen is Kappa, and Kappa is only good at pass blocking, he leaves some things to be desired for run blocking.
I really think this is a scouting problem more than anything else. Whoever is in charge of finding our draft picks and free agents needs to be fired.
That said there is alot on coaching here too, Karras, Cappa, and OBJ all have superbowl rings.