It sounds like you're trying to evaluate him as a 10 year veteran. His passing as a *rookie* was fine and about at the level you would expect. In 2007, he improved on his YPA, yards, massively on his % (which, combined with YPA, screams "better passer"), but suffered an increase in INTs. Despite this, a slightly better QB rating.
No, he wasn't a good passer in 07, but he had arguably the worst WR group, an overweight lazy RB, and an OC who had no business being in the NFL. Despite this, there were some areas even in passing that he did better at than KC did last season. As a 2nd year guy who probably shouldn't have even started at all in his first 2 years like Steve McNair, all things considered, he wasn't going too badly.
And what's amazing is that about sums up what we have seen from Vince Young the QB. It's easy to forget that. Had he not been injured week 1 2008, had Kerry not defied his history and failed to play efficiently, maybe we'd be looking at a totally different situation right now for Vince.
He deserves criticism for how he handled things and he may be out of luck with the Titans, but he's not some closed book of a QB who has had years and years to develop his passing. I fully expected Vince to take a good 4-5 seasons before being able to do damage as a passer just like Steve did, and from I remember that stance was a popular one coming into the league, but now it seems there is an all out attack on his abilities as soon as an opportunity to do so arrised, even if that opportunity is far more related to sideline demeanor than anything.