Karlsson= Generational talent
Zibanejad= Top 5
Zibanejad is not a top 5 talent, but yeah we were lucky enough to get Karlsson and thereby not needing to tank to get an elite talent in the league that is usually found in the top 3 of a draft.
With that said you don't need to tank to make a great team. Realistically look at any draft and you can find players that were taken either late in the first round or in the later rounds that has ended up as good or better than most top 30 picks. It's just a matter of having a great drafting team (Karlsson case in point).
I mean, in theory from 2009 to 2004 alone if someone really had the best scouting staff available you could have all these players without ever getting better than a 15th overall pick:
Erik Karlsson (15th)
Jamie Benn (129th) or PK Subban (43rd)
Ryan O'Reilly (33rd)
Claude Giroux (22nd)
James Neal (33rd) or Keith Yandle (105th)
Alexander Edler (91st)
That's not even including all of them just the ones that stood out right away. You don't need to tank to build a great team and Ottawa is an example of that, too. Build smart and you can build while winning -- which is what Ottawa should be doing if they aren't injured.