Gillies' worst "move" does not involve specific trades, FA signings or hiring snafus. It involves not necessarily learning from Pat Quinn's mistake in the mid-90's and building a team based on the promises the NHL made in how they were going to change the game. In the Mid-'90's following the Stanley Cup appearance against the Rangers, Quinn went for a more smaller, skllled team because the NHL promised it wanted to get rid of "The Trap" and deal with the growing problem of obstruction in the neutral zone. Regrettably, the opposite effect happened where New Jersey rose to a dominate team in the playoffs with that style of play.
Gillies made the same assumption. He took the league at its word that they would maintain the game to be officiated the same way in the playoffs as it would be in the regular season. Granted, our power play came up lame in the Cup final in 2011 but the same promise calling all infractions by the league was made in 2012. However, since that time, the officiating has obvious become "hands off" during that second season and, as a result, the Canucks could not compete with the larger teams that could get away with more physical play. This point was observed and made clear by many media outlets (TSN, CBC, SportNet, etc.) when witnessing this style of play. Since this time, Gillies has tried to play catch-up to re-tool/re-build/re-model this team on the fly to compete while still being competitive. That has been his big mistake, but it's a mistake not because of his abilities, but due to taking the word of the league that it would take the game to a certain direction and not following through all the way.