Ehh, I think the importance of this is a bit exaggerated. Generally, yes, you do need to have some good later picks to be successful. Yzerman in Tampa, for example needed picks like Point/Kucherov/Cirelli outside the first round to get that team to Cup contention. But let's also be very honest here... Yzerman's first round drafting in Tampa was absolutely f***ing abysmal. They drafted a franchise goalie, but outside that you had picks like Koekkoek, Connolly, and Cal Foote that did not pan out at all.
That's a stark contrast from Yzerman's drafting in Detroit. His 2019, 2020, and 2021 firsts are all core players. Potential until proven is just that, potential, but Cossa and ASP both have high end/elite potential. Kasper/Danielson both look like good two way centers who will, at worst, stick in the NHL as role players.
And then you look at a team like Colorado. After getting ROR and Barrier outside the first round in 2009, their drafting outside the first round has been absolute shit. Granted, Detroit doesn't have a MacKinnon or a Makar in their organization.
Colorado's drafting outside of the top 10 & 1st round has been shit, you are 100% correct. They made some great trades and undervalued UFA pickups to get them over the top in addition to their top end guys. Vegas was an expansion team and got super aggressive to improve their roster via trade & UFA. Florida has historically been the worst at developing talent in the A, so Zito pivoted to getting super aggressive to fill holes instead of getting complacent & being hopeful about middling to meh younger prospects.
In general though, you do need to hit on some non 1st round picks to put you over the top to get a Cup or Cups plural. Dating back to the Red Wings 2008 Cup, here are some 2nd-7th round picks that were integral to Cup wins:
Datsyuk, Zetterberg, Letang, Byfuglien, Keith, Bolland, Hjalmarsson, Brouwer, Marchand, Bergeron, Krejci, Lucic, Voynov, King, Martinez, Quick, Clifford, Crawford, Saad, Shaw, Toffoli, Rust, Murray, Guentzel, Holtby, Stephenson, Parayko, Edmundson, Dunn, Barbashev, Binnington, Point, Kucherov, Palat, Cirelli, Killorn, Joseph, Colton, Hague.
Like I said, being aggressive in trades & UFA is very important as well, and you obviously need to hit on your 1st rounders, but you do need to hit some doubles if not outright monster tank home runs to help you over the top, at least in most cases.