I don't know why people resort to this type of argument.
Because some people understand what the team wants to do better than others.
Detroit has no interest in making trades for mid-level players they intend to retain long term. Those trades are very difficult to win in a macro, multi-year sense given how efficient Detroit is in getting exactly that kind of player in the draft. They will make trades at the bottom for spare parts and they will make trades at the deadline for rentals.
For a guy they want to keep, they target them in the offseason as a FA. If they can't land that guy then, they (rightly) presume they'd have had a hard time keeping him after they traded for him.
Detroit can, has and will continue to go to the max on top tier guys who come available, but absent that opportunity they are content to play the averages and coast along... at least that's been the case in this run-up to the new building. On the far side of that, who knows?
Absent an improvement to their top tier, spending organizational assets to get a mid-level guy accomplishes nothing and comes at a long term cost, namely the lost assets moved out in the deal. This team with Fowler (and without the combination of NHL and futures needed to acquire him) isn't really any better now than it currently is.
Why not preserve both those current and future pieces for use in a future where the team might actually have a new top tier player, and hence a more pressing reason to make a push forward of futures into a current or near future season?