Nobody. When your goal is to go far in the playoffs, you don't trade away stars for futures, you keep them to the end to try and win. If they traded Marner 1 year ago for picks and prospects, they would have done worse last season.
Look at Florida. They lost Montour. They will probably lose 1 of Ekblad, Bennett, or Marchand. It's the cost of trying to win. Yeah, they won it all, but there are plenty of teams in the same situation that didn't go all the way, but it was worthwhile to try.
Contenders pick up UFAs to be at the trade deadline all the time, and lose them to free agency.
It's just how it goes when you're a contender. You add and keep stars, to load up each year, and worry about the consequences later.