That 6th round pick was actually used as part of the deal to move up to #12 to get Fletcher Cox. I don't know whether a 6th round pick 16 choices later would have foiled that deal... but I suspect they could have figured out something. Point is, the Eagles didn't get much for Justice. At the time, that really wasn't a huge deal because they were going to release him anyway.
Plus, they had Jason Peters on one side and Todd Herremans on the other and felt pretty good about that. Then, things kind of went to hell. Peters tore his achilles after the draft and the initial push of free agency. So they were forced to scramble and sign Demetress Bell.
Then of course Bell didn't even win the job out of camp. King Dunlap started, wasn't particularly good, then got hurt. Bell played well in his first game filling in but has struggled since. Todd Herremans, meanwhile, has been a shell of himself and Jason Kelce got hurt creating a big hole in the middle.
In short, the offensive line is a mess. And guess what? Winston Justice isn't.
According to Pro Football Focus' game charting data, Justice has given up just 2 QB hurries. He's kept his man away from the QB on 99% of pass blocking snaps, which is the best in the NFL.
Meanwhile, Demetress Bell comes in at 6th from the bottom in the stat. He's allowed 24 pressures this year, which is basically 1 QB hurry every 10 snaps.
Now, this is clearly just hindsight. There really weren't many Eagles fans, if any, that questioned the move to jettison Justice. I certainly didn't think it was a mistake at the time. Plus, there was no way the Eagles could have foreseen the injuries on their line.
But still, it would be nice to still have Winston Justice right now.