I get it, trading is trying to improve your team in one way or another. But you have to consider if the other team would improve as well.
In your OP, Carolina gives up Lindholm and a 1st for RNH and a 2nd. The 2nd is obviously a huge downgrade from let's say the 11th overall pick. And does RNH improve Carolina that much more than Lindholm? Also consider that the extra $2 million RNH is probably costing Carolina limits them that much more.
If RNH was a consistent near PPG player, then I get it, but he hasn't proven to be that while playing with some ultra- skilled players in his career like McDavid, Draisaitl, Hall and maybe you throw in Eberle (who was a good point producer). Carolina has Aho that might be considered in that category and that's it, so RNH would need to do more with less in Raleigh.