Wallinder is, in fact, not a RD. You're mixing him up with Willander, who Detroit does not have.
Or you're taking the fact that he can play RD as he only plays RD, despite LD being his typical position.

Wallinder is a LD and has always been.

Yes, I made a Name mistake. I was thinking of the other one

As a wings fan, I also think it's on the weaker side, but that's not the point. Detroit isn't ready to compete for a cup. Trading a pick that is likely to be 10-15, and one of their top D prospects, who will be in the NHL in 2-3 years when they are ready to compete, for a guy who isn't a superstar D makes no sense. Hanafin is great, and I'd love to have him. And maybe you're valuing the player correctly, but that doesn't mean this trade is a good trade for Detroit or makes any sense for them.

There's more to things than just "Wheel team D bad, give me lots of stuff for good D"