The OL has played fairly well, overall. They are small at guard, so they struggle some with the interior run game. But they are a decent group that is improving. Plus the coaches have made good halftime adjustments in every game. And although they're not dominant, per se, not all of the offensive woes can be blamed on the OL.
For starters, the team needs RBs that can hit the hole -- or the crease -- when it opens. Illinois' RBs are not that quick as a group. At times a RB has failed to hit the hole before it closed up. I can think of one play, in particular, against UTSA that looked like it was "there" for a breakaway, but the RB got beat to the crease by the scraping LB. At other times the RBs don't see the hole. How often have you heard commentators discuss a great RB's "vision."
Then there are times when the OL and TE are simply outnumbered at the point of attack and cannnot block all of the defense, which has stacked the box with 7 or 8 (or more) defensive players--because Illinois has NOT demonstrated the ability to throw the ball effectively to loosen defenses up. Illinois QBs (whomever is in the pocket) is going to have to trust their arm more and give #1 and #6, as well as #82 and #87 a chance to go get the ball! The QBs need to put some trust in both their own capabilities and the big play talent on the roster.