Maybe people will look at it negatively if that happens, but I think that would be a flawed way to look at the trade.
A lot of what San Jose gets from the trade is based on paying for chance, so we can't just eliminate the value (at the time of the trade) of that chance, even if it doesn't work out in the end. The chance of seeing how far they go by adding the absolute best rental that has been available to any team in recent memory, and the chance of having the inside track to sign this generations best defenseman,
None of the pieces they gave up hurt them at all. This doesn't mean we didn't get pieces that will help us given that Karlsson was gone anyways and it was presumably the best offer, but it was basically an HFBoards trade proposal in "Let me list six pieces I don't care that much about so I don't have to give you a really good piece!". If someone made that same proposal six months ago, it would have probably been locked and an HFBoards moderator would have phoned the original poster's ISP in order to request that they block HFBoards from their service.
San Jose getting the opportunities they've gotten with Karlsson (Playoff run, inside track to re-sign him) without hurting themselves with the return is bonkers. It shows both how badly we flubbed the trade, and how badly other GMs were sleeping on acquiring Karlsson. This trade only ends up hurting San Jose if all three of the following happen. Not just one, but all three. Erik Karlsson doesn't re-sign. The Sharks miss the playoffs in 2020. The Sharks pick wins the lottery in 2020. The odds of all three of those things happening are astronomically low.