Yeah, they have not been successful with the OL, but you can't say they haven't tried.
It's much harder to find quality OLmen than it is quality DLmen, but I think they could've been more successful with the guys they've had. Idk if it's a problem with talent evaluation and development/coaching or just simply not having a consistent identity on that side of the ball.
It's becoming more apparent that the old adage of "defense wins championships" is no longer true. With McDermott at the helm, the Bills will probably always have a good-enough defense and could afford to spend more on the offense.