Here is the way I interpret contracts/ salary cap management/ roster building in the current time period
Signing a guy in UFA can be dicey, as it usually is at least a bit bloated if not an outright overpay
Also the term is usually at least a year or two too long
So say Karlsson has been speaking to Nyquist, Zetterberg does a little digging around through some back channels, Alfredsson gives his old teammate a phone call, etc. and Karlsson decides Detroit is a top destination to land for his last big contract, his big UFA payday deal and Steve Yzerman ends up signing him.
That in general is great! Adding a guy of Karlsson's caliber is amazing, right? Well if you're reading through this thread, you might think otherwise.
His deal will very likely land somewhere around an ~$11M cap hit and will be for the absolute max term, because he is the best D to hit the open market since, what? Chara? It has been a good decade+ since a blueliner of his caliber has hit the open market.
So say we all agree a deal more around ~$8.5M and ~5 years long is "fair" for the injury risk associated and potential decline.
In my opinion, in this current NHL set up, you pay your stars. Rather than have the 5-6 slightly (or maybe grossly in Abdelkader's case) homegrown type guys, who all make ~$500k-1M too much and all have a year or two more term than you'd like, you sign a guy like Karlsson for ~2-3M larger cap hit than you'd care to give him, and pay your replacement level players as close to league minimum as possible. That way, even if Karlsson hits a really downward turn in year 3 or 4 of a 7 year deal and he's playing at a level of say a ~$6-7M defender instead of $11M, you've done your due diligence as a GM and given yourself a little cushion to navigate the last 2+ nasty years at the end of that contract.
I would always choose to pay my stars and let the bottom 6 Fs/ bottom pair D walk in UFA if their ask is unreasonable, it just makes no sense in this day and age. It isn't feasible anymore.
Now, if you look at Yzerman's tenure in Tampa, he doesn't necessarily let his "depth" guys walk. Killorn, Palat, Johnson, Callahan, Miller, Gourde all have fairly substantial contracts, though I'd argue those guys are big improvements on the players that our board take exception to (Helm, Abdelkader, Glendening, Nielsen) so it isn't necessarily an equal comparison, but also he went out and traded for Callahan and McDonagh when they were considered big fish trade targets and gave them a big payday, so that fits with what I consider to be an optimal way to construct a team.
The potential reward of landing a Karlsson even at top dollar is so much bigger and better than the potential risk of letting a guy like Helm walk in UFA and signing or promoting a guy for ~league minimum.