He doesn't suck. He's also not a great QB.
He is a developing QB. He does some things well and some things not as well. He is showing improvement in some of the things he doesn't do so well.
Of the first, second, and third year starting QBs, I would take Luck and Wilson over him right now. And my opinion of Andrew Luck isn't media hype or hero worship. He's a good young QB, but he most definitely has his warts. I'm also aware of the fact that Russell Wilson has the best supporting cast in the NFL. Those guys are still better than Ryan Tannehill right now, but as with everything, context is key.