Hell, even just look at our scouting group, and I know I grouping multiple eras together. Over the last 20ish years, how many top pairing dmen have we drafted? And I'm going to go with pretty low requirements of a top pair guy.
Erik Johnson
Alex Pietrangelo
Colton Parayko
Vince Dunn
Petro is the only guy that you can build a true top pair around. Parayko is someone that you can build a top shutdown pair around, but it's not going to be a top pair that can bring the offense like a Petro top pair. Johnson is similar to Parayko, but a lesser version, I'm ok saying he wasn't top pair quality, but I think he had some years in Colorado where he could be the #2 on a top pair. Dunn is kind of that modern top pair in Seattle, opposite of Parayko, he'll play big minutes, but it'll be the offense, not the defense.
Even a team like us that drafts above average will not find that many outside of the very top picks. With Jiricek and Lindstein, and a heavier focus on the position in recent drafts, we'll see if it changes, because more lotto tickets, will improve your chances. But, it's not as simple as just draft more and you are guaranteed to hit.