You can't blame anyone for picking Tua or Jackson, really.
Tua was considered the best QB prospect entering the season and only fell because of the injury and because Burrow played out of his mind for LSU. Herbert was considered very, very good, but there were plenty of questions about him putting everything together; to be honest, those questions still exist. And Tua has had moments where he's looked like the better pick.
It wasn't a dumb pick or a bad pick as much as it might have been bad luck.
We needed an O-lineman and Jackson at that point was the highest-rated guy on the consensus board at that position when we picked. Unfortunately, there were a lot of other more appropriate guys if you were going BPA at that pick or probably at least the next five. But Jackson had untapped potential, too; he was the appropriate pick unless we traded down there. Either he was a bust or coached into a bust, but that's hindsight.
Igbinoghene made almost absolutely no sense. I know people will say X was coming off an injury and we didn't know about this or that. IMO, we were a lot better at corner even considering that than we were at a bunch of other positions. He was a major reach and, if you like him that much, trade down, get the insurance of another pick somewhere down the line, and take the risk on him at a more appropriate spot.
The Iggy choice was so bad that even if Tua hit perfectly and Jackson turned out to even be just a serviceable starter, you'd be right to question the competence of the guy making that pick. The first two were no-brainers. Iggy was the pick of someone with no brain.