If center depth is so key, why couldn't the Avs get anywhere with Duchene, ROR, Stastny, and MacKinnon that year? They couldn't even beat the Wild that year. And even the year after, Stastny was essentially replaced by MacKinnon, and we didn't even make the playoffs.
At the time, we all said it was because our defense sucked. I don't think we were wrong about that, the defense DID suck, and it held us back a ton. As Seph was saying, we basically traded our center depth for defensive depth, and we're a much better team for it.
I definitely buy that center depth is important, but it's not everything, because if it was the Avs would have been contenders in 2014 and 2015.
That series specifically was lost by shaky goaltending and an already rough defense that was missing Tyson Barrie for four games. Matt Duchene also missed five games, and it shouldn't be forgotten that Roy was arguably one of the worst coaches in the NHL at that time.
The reason things totally fell apart in 2015 (missed playoffs) was because of a brutal off-season by Roy and Sakic. PA Parenteau and Paul Stastny out; Daniel Briere, Jarome Iginla, Brad Stuart in. Then, Jamie McGinn missed nearly the entire season. Add it all up and you get this line-up on a nightly basis:
Tanguay* - Duchene - Iginla
Landeskog - O'Reilly - MacKinnon
Talbot* - Mitchell - Everberg
McLeod - Cliche - Briere
*These two frequently flipped due to terrible depth
Stuart - Johnson(missed 35 games)
Hejda - Barrie
Holden - Guenin
Varlamov/Pickard/Berra
Follow that up with what has proven to be a debacle of a trade: Ryan O'Reilly and McGinn for JT Compher, Mikhail Grigorenko, Nikita Zadorov, and a 2nd (AJ Greer) + sign/trade for pending UFA Carl Soderberg.
In the post-mortem, it's pretty easy to see how a team with great center depth went from 112pts -> 90 pts -> 82 pts -> 48 pts. Several missteps were made, and I didn't even mention yet about the prospect pool being bone dry at that time (three first round misses in Hishon, Siemens, and Bleackley).
Long story short, we can't say good center depth isn't the key to winning based on a few disastrous years by the Avalanche organization. I'm obviously happy how things have worked out long term, but Colorado definitely got burned in the O'Reilly trade, and there was certainly a good amount of luck involved in the Duchene trade (Girard being as good as he is and Ottawa's 1st being as high as it was).