Do people think teams like Buffalo, Florida, etc didn't have these same rebuild fantasies? Keep this guy, move this guy for a younger, better version of himself, get a ton of firsts and we're winning the cup in 5 years!
Look at the teams where rebuilds have worked fantastically and find the ones where top, top players being picked in the first 3 or so picks of deep drafts didn't play a huge role. Pitt, Washington, Chicago, Toronto, Edmonton (sort of)... If you don't get Crosby (1OA and generational), Malkin (2OA), OV (1OA and generational), Toews (3OA), Kane (1OA), Matthews (1OA), McDavid (1OA), etc, tearing it down with plans to be actually competing for the cup again in the near future is nothing more than a daydream. And even then, you can end up getting the Yak type players who are highly touted but turn to crap when all is said and done. Even Edmonton, with McDavid, the best prospect of our time, and so, so many other 1OA picks still doesn't look ready to compete anytime soon.
I'm not saying don't get younger, but these talks of committing wholesale to a rebuild, moving everyone who is slightly older for picks and throwing caution to the wind only to end up even better in a few years are optimistic at best. I'd way rather do what they're doing now. Make moves for the future when they're there to make, but don't go overboard trying to tear down todays' team for a fantasy version of tomorrow's.
Edit: look at league standings right now, the bottom 4 teams have all been rebuilding by this wholesale logic for a number of years and have little to show for it. Edmonton was a playoff team last year, but they got McDavid, a prospect without an equal even on the horizon.