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.