...I agree with the bolded and underlined part, but as you said, Leary is the only example of a guy we have developed who has even pushed for a starting role in over a decade (that we could both think of off the top of our head).
It's been a really, really long time since we've developed a really good OL from scratch, and longer if you don't count the no-brainer top-10 pick variety of player. And I understand the frustration with it, because I share it myself. The fact that guys like Kowalski (injury) and Arkin (questionable strength) have been on the roster as long as they have been and aren't seen as potential up-and-coming starters for us down the road drives me up the wall, too.
I do think that very recent history looks more promising. Leary, as I've said. I think Costa and Parnell are success stories of the sort you have to have to have good OL depth. Frederick and Smith were expensive resources, but I don't think we missed on either of them. And I think OGs are important, too, just not as important as the other holes we've been concentrating on fixing recently.
I'd like to see us address the OG position the way we did the S position last year. Basically, we develop one starter from deep in our bench (like we did with Church) and then bring in an experienced vet (Will Allen) to hold down the fort. And then use mid round picks to add high-potential players you think can develop into eventual starters for you (Wilcox and Johnson). Throw a couple college FAs you like into the mix to push the middle-rounders.
The thing is, we need our premium picks to replace the DT/DEs we're going to lose this offseason. We need a QB to start developing. And it's insane to think that picks and cap dollars are wasted when they're spent at the CB position. I'd *love* to be able to add a premium player to the interior OL, but if we do that, it's going to be at the cost of a player at a position of greater need or at a salary cap expense that makes a second contract for a player we really really like difficult.
Personnel in the NFL in a salary cap era is a zero-sum game. I'd rather skimp at the positions where you've got the best chance of filling the roster with a value signing or a value pick. That doesn't make me a 'pollyanna.' It doesn't mean I'm not in favor of upgrading our interior OL where we can, or that I mistakenly think Mack and/or Livings are better than they actually are. And it doesn't mean that I don't agree that we've got a recent track record of not developing quality OL starters from the bench.
Looking at how the organization under Garrett churns the roster at position groups until they get options they can work with, and given that we've just brought Callahan in recently and that other positions along the OL are gradually improving, I'm willing to give them the benefit of the doubt that they'd eventually find options for us that will work. Especially because I don't really see where we've got any other good options available to us.