I don't think it's that simple as there is a luck/timing element to it as well. Most rebuilding teams don't actually finally reach their success by design it tends to be by accident.
Colorado was supposed to be done rebuilding after they got Mackinnon/Rantannen etc. They were building/pushing forward until they had Roy leave them right before the season, had a terrible year and there was Makar sitting there for him. If Roy stays there's a good chance there is no Makar and maybe even no Byram (Duchene asked for a trade because of this season).
Same thing with the Lightning. Had their core go the Eastern Conference Semis then crash out, finish 3rd, get Drouin, flip him for Sergachev and then voila.
Oilers got their number 1s in what was a pretty weak cycle of drafts (McDavid excluded of course). Bit of a similar story to the Flames as 2013 and 14 were not strong drafts. So Flames bottomed out but didn't really get the caliber of player you'd normally expect. There is luck (and to some extent planning) involved.
I think at the end of the day we make it seem like rebuilding is easy. You lose, you get good players you see success, it's such an easy equation. Yet there are so many variables that go into it that I don't think get enough attention. Regardless of my personal opinion (disappointed to say I am not currently a Calgary Flames owner) I can just understand that if i'm an owner getting pitched a rebuild idea it's not exactly illogical to not want to go ahead with it as there are plenty of uncontrolled variables that make it risky to a certain extent. Just don't think it means that mediocrity is ok.
As i've said I would have been fine if they did it and 2 summers ago I was ready then too because last year's draft and this one are so good that the timing made sense. I think they'd have success with it but the owners felt differently and I just don't think it's fair or right to say it's because they are ok with mediocrity.