"So we all heard about the gains in the weight room this off season and reasoned that this line will now be good. But they are, once again, awful. "
You pointed out pretty obviously there's a disconnect between football ability and several things kids can be rated on with an arbitrary star system.
Great gains in the weight room this past off season can be one of them. And its pretty plain that your assessment is in the now, and not about the future. Which is sort of at odds with the rest of your post about building kids from a smaller more athletic size. Those guys being very nearly graduated, its hard to say exactly what screwed them up, but likely the real answer is they are better than we are giving them credit for but very inconsistent, and having a couple of staffs did them no favors either.
The whole NFL "workout warrior draft pick bust" is a pretty regular occurrence. While great gains in the weight room is often a trait of good football players, just because some snuffy makes gains in the weight room doesn't mean he's about to be a good football player ten minutes later. Correlation is not causation.
This happens alot on this board. "Bunch will be a more than serviceable backup because he's a great fit for Frost's system and he can run! He never would have been all that good under Riley!".
Two weeks after camp, folks sorta learned the hard way that just because Bunch has a skillset fit for Frost's offense, doesn't mean he's actually very good at using it. People have a bad habit of assuming that if you need a certain skillset at a position, and you go out and find that skillset in a person, that person will automagically blossom into a good to dominant player (often in an unreasonable amount of time) because "fit". Fit is not the only thing that matters.
We don't assume that when we buy a hammer or a tv or a car, but we do football players. Everything on Amazon has star rankings too