Do we have trouble with developing D though? We haven't drafted a D in the top 15 of a draft in my time as a Wings fan, that I can recall, which is nearly 30 years. Many teams have bad D draft records, because unless you get lucky, getting an awesome blueliner in the 2nd and beyond rounds is very hard. Being good for so long is a much overlooked reason why it looks like we can't develop D. Smith and Kindl are it, are they not, for 1st rounders and so we went 0 for 2 in the past many years, and that is par for the course when drafting players. Don't know the numbers, but most drafted players do not become awesome players, so getting really good ones is hard.
Drafting and developing is mostly luck, like we had getting Z and Pavs in ridiculous low rounds of 6 and 7, and sometimes you get a bunch of it, and sometimes you don't. Obviously some scouts are indeed better than others, as are coaches, but players developing into something prominent, is so much about luck. When developing, did the get hurt, have a coach that wrecked their confidence, have something bad happen in their family that affected performance, and so many other things that can affect how a player grows into anything of prominence.