This is definitely the part that boggles my mind the most with people defending how good Bergevin is based on his trade record. If he's THAT great at making trades, and the team is THAT bad, he must be freaking aweful at everything else, because he did not start from a bad position at all. He started with a Norris winner, a Vezina winner, a 3rd overall pick and a winger that was going to be top 5 in total goals over many seasons. The team was not perfect, but it was competitive and had key pieces, was mainly just missing a top center to be a serious contender.
But it really boils down to no vision. All his trades, with the exception probably of Danault and Pacioretty, are replacement trades. He creates a hole somewhere or replaces a player that either got traded or was falling off. It's trades that allow the team not to just become significantly worse than it was before, but they do not improve compared to how the team already was. Signing Radulov to 8M per season and keeping Sergachev would have been FAR better for the team than trading for Drouin. We would have a much better Left D with same quality (if not better) wing. So it doesn't even matter if you consider the trade a win, or a wash when looking at it player for player. In the end, it's a move that made the team worse.
Domi vs Galchenyuk and Weber vs Subban might be good trades if you compare how both players involved in the trade perform currently. But Subban before getting traded was as good for the Habs as Weber ever was, and Galchenyuk wasn't much different than this year's Domi. This year's Domi is better than this year's Galchenyuk, and this year's Weber is better than this year's Subban, great, but the team didn't improve as a result of those trades, it just didn't get worse.
Improving a team isn't winning 1 for 1 trades in a vacuum. It requires adding to the overall quality of your roster, knowing that some of that quality will go down and some will go up in the future on its own depending on the age of the players involved. Trading players going downhill for players trending up is definitely something you want to do, but it doesn't mean that your team improved in itself, it just prevents it from degrading.
Bergevin showed he can trade well enough to maintain a team in mediocrity and not fall off all the way to the bottom of the league like the Red Wings did. But the team has been gradually getting worse over his tenure, meaning he's just aweful at other things necessary to build a contender. Stop defending his trades in a vacuum and just look at the big picture, the team is clearly not better with him at the helm for so long.