That's the problem. The pick wasn't made for today. The pick was made for yesterday. At the time, Henrik was getting run like crazy, and the team hadn't really developed a toughness yet to stop/defend it. The team was seriously lacking in that regard. The Rangers needed to add that element and really felt a need for a tough guy on the back line. The problem with that rationale was that you were making the pick based on a need in 2010 knowing that the player wouldn't be in the league for a minimum of 3 seasons. Fast forward to today, and toughness isn't a major issue (although more is always welcome), but overall talent is. That is why you draft BPA, because it can be hard to see what a need will be years down the road so you roll the dice with the best player/asset that you can get.
I wasn't a big fan of the pick at the time. However, I've warmed up to it, and think that McIlrath can be a nice addition to the roster down the road. I still think it's too early to rate this draft, because most/all of these guys are not finished products yet.
Lastly, to sit around and complain about this pick is a waste of time. It gets rather tiresome after awhile. This draft happened over 3 years ago, so let's root for the guy and give him a fair shake rather than sitting around moping about it every time Tarasenko scores. This pick may not be the best pick, but when you consider the entire body of drafting over the last 5 or so years, then you have to see that they've done an excellent job. Can you name a team whose done more with similar or worse picks? MAYBE 1 or 2. This team is young, hungry, and has an identity. There are holes for sure, but I see no real issue with drafting when they've developed more players in the last 5-6 years than they had done in about a 15 year window prior when Mike York was arguably their best drafted asset.