Prime MAF single handedly lost several playoff series with Crosby and Malkin at their peaks. He was not a difference maker in winning a single series between 2008 and the Capitals series in 2017. But he was a difference maker in losing them games and series.
And while Fleury was good in the 2009 SCF, he was not the primary reason they won games 6 and 7. The Penguins commitment to team defense strangled the Red Wings attack. Hell, in the final minute of game 6 it wasn't Fleury making multiple goal line saves to preserve the lead, it was Rob Scuderi after MAF slid out of position.
He was a difference maker in 2009 when he put the Penguins on his back in game 6 and 7 and delivered a Cup to Pittbsurgh, otherwise the parade was ready to go in Detroit.
The other years where he slumped, sure, but that just goes to show, Crosby and Malkin couldn't do shit in the playoffs without really good goaltending and they regularly went out in round 1 or 2 those years.
There's no team that McDavid's been on that Crosby would win a Cup with. He got way more run support from all his goalie's in the years he won, not to mention Malkin, Letang, and then also Kessel (this would be like adding Eichel to McDavid and Draisaitl).
This is the Pens goaltending in the 4 years they made a Cup Finals
2008:
Round 1: .955 vs Ott (MAF)
Round 2: .924 vs NYR (MAF)
Round 3: .939 vs Philly (MAF)
Round 4: .923 vs Detroit (MAF) lost
2009:
Round 1: .922 vs Philly (MAF)
Round 2: .878 vs Washington (MAF, Washington had .895)
Round 3: .924 vs Carolina (MAF)
Round 4: .913 (MAF) vs Detroit
2016:
Round 1: .955 vs NYR (Murray)
Round 2: .926 vs Wash (Murray)
Round 3: .904 vs (Murray) vs. Tampa
Round 4: .920 (Murray) vs San Jose
2017:
Round 1: .933 vs Clb (MAF)
Round 2: .921 vs Wash (MAF)
Round 3: .946 vs Ottawa (Murray/MAF)
Round 4: .931 vs Nash (Murray)
That's 4 playoff runs and a whopping two poor playoff rounds total in goaltending out of 16 playoff rounds. I'd say that's pretty f***ing amazing. And for one of those Washington also had sub .900 goaltending.
Not only that in those runs when Pittsburgh ran into like a game 7 ... quite often it was their goalie and NOT Crosby or Malkin who was their best player in a winner takes all situation.
Like 2016, the "bad" playoff round Murray had against Tampa? In game 7 he was very good with a .941 save percentage, Crosby had 0 goals, Malkin had 2 secondary assists. Brandon Rust scored both goals in a 2-1 g7 win (go figure).
2017 ... Pittsburgh beats Washingon in 7 games, in game 7 MAF has a *shut out* 2-0, Malkin zero points, Crosby one secondary assist, Rust with the game/series winner (this dude is underrated). Etc. etc.