This can be said about any position.
Who had "the Oilers will sign Viktor Arvidsson for 4 million dollars to play with Draisaitl and his numbers will be worse than Kailer Yamamoto" on their bingo card?
There's no guarantee anywhere unless you are trading for an elite player and even then there are question marks, see: who had Mikko Rantanen will be traded to Carolina and be producing poorly, less than Necas on their bingo card?
You do the best you can and do as much homework as you can pro scouting wise. We had no idea in 2006 that Dwayne Roloson would take us to a Cup Final exactly, I think at most the feeling was we were a team being held back by poor goaltending and now we had a fair shot. And sure enough, the team took off in the 1st round of the playoffs on Roloson's back and shocked the hockey world.
Things like Adin Hill aren't that impossible to see could have happened, his numbers were quite good on really bad teams. Vegas has a good d-corps, at some point it's like throwing a spark on a bunch of dynamite, eventually you'll get an explosion if you throw enough sparks.
Everything is a guess, what seperates good scouting departments from bad ones is you take a look at certain variables. We used to have incredible, elite pro scouting in the days of Glen Sather where he saw something in players like Doug Weight that no one else did, unfortunately those days are long since past and our scouting has been awful for decades at this point.
When you have a team weakness that is obvious, you do your best to fix it. If it doesn't work, then you try again. It isn't more complicated than that. Things like "well, how about we just whine and cry and pretend the roster issue is not a problem and it'll just go away on its own" is not a strategy.
