What could Boyle teach Smith that Kronwall can't? Kronwall is the better player. He's had more success. Plays a gritty/offensive game (the way we'd like Smith to play). And he's a lefty, like Smith. Boyle and Smith have very little in common aside from the fact that neither are likely to score 20 pts. for the Red Wings next year (sorry, I had to).
Like I've said before, you can justify it however you like, but adding mediocre players to a mediocre team just leaves you mediocre.
Okay instead of just being negative in response, why not offer up what you think they should do?
Boyle isn't mediocre, even at 38. He had an off-year last year and still posted 36 points. He is a known commodity. Niskanen is not (not saying I wouldn't like Niskanen), but I can see the inherent risk in bringing him in for 7 years at 6 per. Whereas bringing in Boyle for 2 around 5 million is much less of a risk. Ehroff is another strong candidate but who knows what he'll ask for and what kind of term he'll want. They are also gunning for a righty, so that makes things a little tougher to sort out. Basically gives you Niskanen, Boyle, and Gilbert as the top right handed candidates. I'm not so sure that Gilbert fits the top 4 d-man mold, but I could be wrong, I'm not super familiar with his style of play. In the end, your assessment of Boyle is far off base, and like any veteran, he can teach the younger guys (like ANY veteran can) if they feel so inclined. It's not a discredit to Kronwall, just an additional guy to play off of and get experience from. You're entitled to your opinion, but when the facts say otherwise, it's hard to see things the same way. We'll see.