Trevor Lawrence isn't the problem. If anything, he's one of the reasons why they're able to make something out of nothing all too often.
The game against the Browns, where they had to drive the entire field, down by 3, starting at their own 2 yard line, was the ultimate display of the ineptitude of the line. The left side of the line got overrun, and the result was a safety.
The offensive line was terrible last year as well. They were arguably the worst at running the ball last year, and their pass protection wasn't much better.
It wouldn't matter if you had Joe Montana or Tom Brady at the QB position, or Emmitt Smith at RB. If the offensive line can't perform, then the most talented quarterbacks and running backs will look like journeymen out there.
The lone exception was probably Barry Sanders...