Constantly picking top 5 and tanking doesn't guarantee success either. Hit on your top ~40 picks, get occasional depth from the mid rounds, and smart signings/trades are how the best teams are built. Lately the Avs have done well on the first part... the rest is mixed... some good, some bad.
Tanking helps if the player you pick is Crosby or a Kane or McDavid. Lets face it, Duchene and MacKinnon are good players, but neither one is creative enough play maker to produce no matter who they play with, and make their line mates better unless their line mates are star players. Duchene and MacKinnon are more of north, south, fast, flashy players, but they don't have that, puck possession, hanging on to the puck, patience, creation in the offensive zone game.
You put anyone with Kane, Crosby or McDavid, you'll get the same results and they can make average players on their lines look like stars, Duchene and MacKinnon aren't capable of that and that's why its so hard finding right players for both to have chemistry with.
If Avs tanked, won the lottery, and picked McDavid in 2015, they'd make the playoffs every year from 2015 without a doubt.