Based on the evidence, the rebuild has not started. This is just a bad team that is quite directionless. Management that thinks they can compete for the playoffs every year, but the results just aren't there.
Throughout the last several years the Canucks have loaded up the team with veterans. Even last year it was stockpiled with veterans. During the season they traded away a draft pick, and they traded away a prospect (for now pieces). They have not traded away a player straight up for a draft pick since June 2015 when they traded away Kevin Bieksa for a 2nd round pick, but then a month later they flipped that draft pick to bring in Brandon Sutter. This team has not acquired a pick in the top 3 rounds, for a player, and kept and used that pick at the draft since they got a 1st round pick back as part of the Ryan Kesler trade. The lack of draft picks acquired does not suggest that this team is in a rebuild.
Every year the Canucks load up on veterans. Some people will point to the team adding a couple of rookies or youth to the lineup, but I easily counter that by pointing to the fact that every team in the NHL adds rookies and youth to the lineup. That was something that our teams have typically had problems doing, but if you actually look around the league, including the contenders, young players are incorporated into their lineups with regularity. The Boston Bruins are an example of this. They've been adding youth into their lineup steadily in recent years; however, they clearly are not in a rebuild. They did an aggressive retool in 2015, or a one year mini-rebuild perhaps (much more than anything Benning ever did here); however, they have kept the majority of their core and have not been afraid to put their youth in key roles. While Benning is too busy focusing on overloading the team with veterans and 4th liners, Boston focused on adding skill players and giving opportunities to their top young players to play with those skill players. They avoided overloading their team with aging veterans.
Some will point to our prospect pool as an indication that the Canucks are rebuilding, but that over simplifies the Canucks situation and also ignores facts. First of all, any team that has been as bad as the Canucks have been will have an improved prospect pool. Any team. That's just the nature of how the NHL draft works. Bad teams are rewarded with higher draft picks. Our drafting in other rounds has not been entirely incompetent either, so we are starting to accumulate some decent prospects. That's not the result of a rebuild, that's the result of the team just plain being bad. Furthermore, we're adding some decent prospects that are on the same level that other teams have plenty of as well. Just look at Tampa for example. They've been one of the top teams in the league for most of Benning's tenure here, yet they also have a stockpile of prospects that I would say is much deeper than what Benning has assembled. That's without Tampa having a single top 10 pick during this time period (Benning has had 4), and with Tampa only having 3 first round picks in the last 5 drafts.
Each year Benning has been here the Canucks have spent to the cap. Last year the Canucks went over the cap due to Brock Boeser hitting his bonuses. It's very rare for rebuilding teams to be this expensive. In some cases you'll see rebuilding teams take on other team's bad contracts in order to add an extra prospect or draft pick, but the Canucks haven't bothered to do that. Instead, every year they are big players in the UFA market, often times adding their own bad contracts. Again, not something you usually see from rebuilding teams especially when you factor in these contracts are multi-year deals.
So, looking at the evidence and how the team has been run, it's safe to conclude that the Canucks have not yet even started a rebuild. They may call it a rebuild, the standings may suggest they're probably in a rebuild, but it's not a rebuild. Instead, this is merely a bad team that has poor management. It's a team that's trending down and is stuck in the bottom of the NHL standings, yet has management that continues to try to make the playoffs every year. The emphasis has not been on rebuilding through the draft, or around youth. The emphasis has quite clearly been to spend to the cap on bringing in as many veterans as they can, leaving a minimal amount of roster spots for youth. They can talk about "doing things the right way" and rebuilding through the draft, but the fact of the matter is they have not bothered to employ this strategy. This delayed rebuild is going to keep the Canucks at the bottom of the standings for a long time, in what will be quite easily the darkest time in Canucks history.