This is basically true, but as the Colts found out, having drafted a great QB in Luck does no good if he's constantly on IR because your OL is crappo. They finally figured that out and their offense was vastly improved in consequence.
"The Broncos OL has been not good for the last 10 years." -- Mark Schlereth.
They drafted Bolles instead of Ramczyk who is starting in the NFC Championship game this weekend. They drafted Ty Sambrailo who flamed out. Aside from that it's been and endless succession of trying to get better play out of a series of misfits and castoff OL because they were always chasing other areas of weakness.
This year they finally signed Mike Munchak who is one of the top OL coaches in the NFL, but he's going to need some decent players to go along with.
They need to decide whether to re-sign Matt Paradis, and we don't even know if Paradis wants to return to a rebuilding team. The rest of the OL is forgettable and replaceable. Bolles has regressed in his second season, and his 12 penalties helped mightily in contributing to the Broncos OL being among the most heavily penalized units in football. He's got to cut that out. The second most penalized Broncos OL? Connor McGovern with 4 holding calls. That's not good, but pales in comparison to Bolles, the tackling machine.
We'll see if Munchak can improve this bunch, but he's highly regarded all over the league as a great OL coach so we'll see.