Arizona already has a Dermott. His name is Jordan Oesterle.
Not interested in your sheltered D.
Jordan Oesterle is 28 years old. At this point, he "is what he is".
Travis Dermott is 23, with a long career of upside ahead of him. I don't think he's a top 2 defenceman long term, but I do believe he's a really solid top 4 guy given the right role (which he's not going to get in Toronto).
In terms of "worth" -- Dermott in theory should be "worth" more than Crouse. However, with the glut of available defenceman, the fact that Arizona needs to add picks, not subtract, the fact that Toronto probably needs to make this deal more than Arizona does, and the somewhat unique attributes that Crouse brings -- I think this deal makes a lot more sense straight up.
Coyotes get a 23 year old defenceman that they can likely throw right onto the 2nd pair alongside a Jason Demers -- somebody who they could probably get for 3 years under $2m. From a dollar perspective, I think you can structure his deal something like $1.3 - $1.6 - $2.2; so you spend less than you would with Crouse over the next 2 years, and get that 3rd "bonus year" at a really good cap hit.
Leafs get a 23 year old that they can likely throw right into their top 6, and get a lot more offence out of him than Arizona has because of the talent they have and the style of play they employ.
Both teams get guys that are under-utilized in their current roles, and both likely benefit from the change in scenery.
Toronto trades Andreas Johnsson elsewhere for futures.