there's just not that many prospects that safely project to be top 6 centers. the few that do are either already in the nhl (celebrini, bedard, smith, carlsson, fantilli, cooley) and will cost a mint to acquire or are basically untouchable (dvorsky, catton, ritchie, lindstrom). you can maybe pry loose a guy like danielson or kasper from detroit or beaudoin from utah or maybe danny nelson from the islanders but those guys are not safe bets to be top 6 guys and might be years away in the case of someone like beaudoin
if vancouver are serious about acquiring a top 6 center who is young the most attainable on the market might be shane wright. seattle have beniers and chandler signed long term and have to make room somehow for catton and possible miettinen and molgaard in their top 6. i dunno what the kraken would want in return though. starts with the first and probably includes either elias nils pettersson or sawyer mynio or maybe lekkerimaki (although seattle is stacked with wing prospects so maybe not)