These are the seasons some former mid-round pick players of ours made the NHL
1) Connor Brown - draft year +5
2) Andreas Johnsson - draft year +6
3) Pierre Engvall - draft year +6
4) Zach Hyman - draft year +7 (drafted by Florida)
Sure, you get the odd Dermott (high 2nd rounder), Gunnarsson, etc who make the NHL within ~3 years or so, but it's not particularly common.
I think the biggest knock on our farm system in recent years has been the number of quality prospects/picks we've moved (Durzi, Grundstrom, 2019 1st, 2021 1st, 2022 1st, etc traded away). Right now we're relying a ton on our mid-round picks, which tend to take longer, and also have a much lower chance at success.
I think it is a bigger issue that we've had 13 picks between the top 10 and top 101 in the 2015-2017 drafts and only 3 of them amounted to any kind of NHLer: Liljegren, Dermott, and Grundstrom. Woll may make it 4. The other issue is that, other than Liljegren, none of them look like they would be difficult to replace with a UDFA or a later round pick at this point. Grundstrom has become a decent bottom 6er in LA, and I think we can sign ZAR or Motte for practically nothing to do what he does.
We are at a severe disadvantage, and are generally not a good drafting team, if we can only hit on first round picks... And not only first round picks, but top-half of the round first round picks. All of our competitors can afford to move off a bunch of picks to help their current team and still find contributors in the mid-late rounds, like Tampa. If we can't, our chances are severely reduced. Of course that does not mean you should move off top round picks for cap dumps or rentals, or generally be reckless with them, either.
But even if we look at the Mrazek trade where we had to move from 25 to 38. Sure, we missed out some good prospects in between 25 and 38, but we still had an opportunity to draft multiple guys at 38 who would have been more than fine value at 25. If we drafted a bust in Minten and there was a guy taken afterwards who turns out great, are we mad at the trade or the fact that even after making the trade, there were guys who worked out that we missed out on?
Another more concrete example would have been when we traded down from 24 to 34 in 2015. Konecny was taken at 24. People, mostly in hindsight, were mad because we traded down from that spot to pick Bracco, Dermott, and Dzierkals instead of just taking Konecny, who is a solid player. However, the Leafs could have made that trade and picked Aho, Cernak, Hintz, Greenway, Siegenthaler, Kylington, or Carlo instead of Dermott, and Cirelli instead of Bracco or Dzierkals. If we got Aho (or even Cernak/Hintz) and Cirelli instead of Dermott and Bracco or Dzierkals, I think people are ecstatic about the trade. In fact, I think people would take Aho/Cernak/Hintz/Cirelli on their own over Konecny on his own, and you'd get two. The issue is less with the trade and more with poor drafting.
Moral of the story is that trading some good prospects and picks is fine if you get the right deal for them and you are strong enough at drafting to be able to find good young players without needing high picks. I would be fine with trading Sandin if we got a good young player in return, for example. Or if we made another Muzzin trade at some point. That trade has generally worked out well for us, even with Durzi, Bjornfot, and Grundstrom working out decently well for LA. But we need to scout well enough to make those moves and find guys like Steeves who may be able to make a guy like Robertson expendable or can be used as a valuable trade chip.