At first, I had the same reaction.
But then I thought about it a bit. I don't think there's anybody who will argue the Oline needs some serious help. But you can't just completely overhaul a line in one off season, especially with over half of it becoming free agents. Starks isn't the best tackle in the business, but he's servicable. The Steelers had three options. They could have hoped he developed into a better tackle and signed him long term, let him go to FA and hope he doesn't find a better deal, or tag him for a year and work on the weaker parts of the line.
I'm hoping that last one is what they decided. Keep Starks for a year, work on improving other parts of the line, and then depending on how he does throughout the season, sign him long term if he improves or let him go.
Feel small yet?