Alex Smith may not be the greatest option, but he's not horrible. The passing game needs weapons - nice to have two decent TEs, Kelce is likely the best option, but the WRs need to be overhauled.
If KC can get away from Bowe and the other spares, that's the way to go. Or, keep Bowe, but you have to have a legit #1 threat and he's just not it. I think he's a solid #2.
This is nothing earth shattering, but Smith is good enough to win with KC, but there's nothing to be trusted with the weapons. Smith is the best option for the near future, build around him with real talent at WR and you'll likely see an improvement.
It's a passing league now and if you can't pass, you're not going anywhere. There are a lot of options out there...
http://www.spotrac.com/free-agents/nfl/wide-receiver/