Ahh, gotcha. Following that logic:
*Don Sweeney of Boston is actually mediocre, because of all the good players that were there before he started.
* Jim Rutherford of Pittsburgh is actually mediocre, despite winning multiple Cups, because he already had Crosby and Malkin.
* Brian MacLellan of Washington is actually mediocre, despite winning a Cup, because he already had Ovechkin.
Keep grinding that axe...
This reminds me of the famous NFL Reddit post where a guy went through great lengths to argue if you normalize Mahome's statistics, he's actually no better than Dak Prescott.
So if you take away all the reasons they win and attribute it to something else, obviously they are all pretty average. I mean, people did that with Holland for years. I've seen people argue he inherited his championship players like Lidstrom and Yzerman and then later got lucky with the likes of Zetterberg. Dude was just sitting around at the right time and right place and championships fell from the sky.
In conclusion, if you take away why a team is good, they are actually average.
Literally no GM starts with nothing. Well, other than like... expansion teams, I guess.