IMO, the deal was more about ridding the Oilers of a really nasty skid mark laden pair of briefs left on the locker room carpet by Peter Chiarelli and aligning the fanbase behind the HolPlANd, which was mixed to negative for his hiring and mixed to slightly more negative on his first foray into free agency as Oilers GM.
The Oilers should've been a contender by now and they're spending more ($500k more a year and possibly a 3rd rounder) to rid themselves of a distracting player that was underperforming and wanted out, for a gamble that Neal can return to being a 20 goal scorer.
Considering how puzzling it is for the Flames, that was probably the only deal out there for Lucic's contract which was said to be unmovable and is completely buyout proof. So doing the nearly impossible only helps Holland get some breathing room from a fanbase desperate for even the smallest shred of management competence and to forget the guy that was there before.
The Red Wings are in a different spot. They don't have the urgency to compete now, and probably aren't ready to start dumping out contracts to big name UFA's. That said, they do have the flexibility to start courting them if the need arises. Franzen, Daley and Ericsson are all likely 100% off the books next summer, and if Green and Howard aren't, it's at a lower cap hit than they're at now. The next summer you have Zetterberg, Helm, Filppula, Nemeth, and Bernier in the same boat. On top of that Helm's NTC is voided for the coming season and likely the next season since they didn't make playoffs. Abdelkaders does the same thing starting next July for the last 3 seasons of his deal. Nielsen's NTC has already slimmed down to a 10 team no trade list. A retained deal to a contender after 7/1/2020 would almost be like signing a veteran 3C as a UFA, with the bonus on not having to pay as much in real $, that is unless Nielsen really falls off in the next season. Nielsen's deal also has some LTIR potential for the last year (maybe two?) since he's only due $1.5M after 7/1/21.
On top of that, as long as Yzerman continues stacking up young assets and draft picks, he could always dangle something in front of Seattle in two years to get them to take Abdelkader or Nielsen if for whatever reason they really need the space.
As for OP's list of candidates:
Stepan - IMO, he's probably still a positive asset. He just turned 29. The Coyotes are probably hoping he can turn it around with a healthier team that includes Phil Kessel this coming season. He had a slow start last season, but in the 20 games before his injury he started to turn it around with 5G 9A in 20 games.
Backes/Dubinsky - These guys are both broken down aging plugs. Sure their contracts come off the books in only two years, but the Red Wings don't exactly have some cap crunch on the horizon that makes Neilsen/Abdelkader a block in retaining needed guys. None of their upcoming RFA's are going to break the bank, and as mentioned before, they have a steady stream of contracts coming off the books in the next 1-4 years. On top of that, Nielsen has been a decent influence who can compliment the development of (and keep up with) young wingers, and Abdelkader can still skate. In the unlikely chance that the Red Wings turn it around within the next two years, those two are probably more useful than Backes/Dubinsky.
Nemeth gives us a still somewhat young (ie, not over the hill) LD who can babysit Hronek, Green or Bowey, and play the PK.
I think he's the placeholder, perhaps, for McIsaac.
These are veteran guys who provide just a bit of stability, defense and smarts to help our young guys develop,
Nemeth is basically a year early "Liljicsson 3.0". A big offensive void Swede that gives them some insurance in their own zone. They also needed somebody to pencil into the 20-21 roster since there's no guarantee that young guys are going to be able to fill the spots opened if/when Daley, Ericsson, Green and Kronwall (if he returns) are gone, and will be tough to compete with 30 other teams to reasonably sign that more than a couple dmen on the UFA market.