Funny how it's suddenly irrelevant to discuss GM performance, after years of every single thread turning into a GM debate.
Maroon is a 4th liner who was dumped this past offseason. He can provide a 4th line impact, some entertainment, and pot the occasional goal, but contrary to your claim, he is clearly not "more valued in the playoffs than Mitchy." Marner is an elite player, his performance and success is not dictated by 4th liners, and every single hockey person in the world would take him over Maroon in the playoffs.
Not really a concern for us, since we can afford good defense and quality depth pieces, like we had for years prior to this one.
We're on pace to get more goals and points from our core 4 than last year, so blaming Tavares being snakebitten doesn't really fly. Samsonov struggled through the first half, but overall, we've still received above league average goaltending this season. We've experienced much worse goaltending over the years. Brodie has struggled this year in a top pairing role, but that's been amplified by our defensive support being stripped. He'd probably be fine in a reduced top-4 role if we hadn't left a giant hole in it and our PK.
Our main roster flaws right now are scoring depth, PKing, defense, and goaltending. Treliving's hands are all over that, with both what he did and what he chose not to do last offseason.