$5M for 1 year would be a good deal. But it isn’t that simple. You have to consider term and age (expected regression) too. With all factors considered, this is not a good deal for what I think is a third pair defenseman who can occasionally step up to second pair duties. He’ll be 35 at expiry.
People get way too hung up about say the last year. We don't care about the last year.
In 2029 the cap an easily be around 105M. If he's reliable enough as a #5 then, your 5's will easily make 3M then. So THAT year, he's overpaid by 2M. He can also be traded with a bit retained, bought out, etc.
So think about the actual meat of the deal. Go look at the D in the NHL playing lights out at 30-34. Plenty of them.