Quoting: A_K
Ask yourself, if getting premium pieces was this easy, why wouldn't every team just rebuild at the first sign of missing the playoffs? You're confusing speculation on the trade market with reality - where a couple of high-end rentals will get traded for a couple of first round picks /across the entire league/ and no blue-chip prospects are traded. These returns are borderline trolling.
This ACGM is largely off base, but bolded is where people really miss.
For rentals:
Chiarot may return a 1st because he's one of the top considerations. People will disagree, but GMs will value a player like that for the playoffs. There might be two defensemen who return a 1st this year, and he
might be one of them. (Giordano is the other, imo.)
If any other rental defensive D is traded for a 1st, Chiarot won't get one.
Lehkonen might be rumoured as a 1st, but he's also not a pure rental. That could put him in a different market. As a rental, he would not return a 1st with players like Giroux and Pavelski available. His RFA status is why he
might be able to garner a 1st, but he's still competing for a limited pool of available 1sts with those offensive rentals.
There are 2-5 1sts exchanged each deadline. Normally closer to 2. Non-rentals are more likely to return a prospect as the main piece. That's where Lehkonen is.
As for Blue Chip prospects, they don't get moved for rentals (usually). Not without an extension agreement.
There's another problem here though. Not every prospect is blue chip. The league average per team is somewhere around 2. Your 3rd best prospect may not be one. Your 4th almost definitely isn't.
People treat every prospect as such and it simply isn't true. Pick two players you definitely wouldn't trade. If you struggle to pick the 2nd one between two choices (and be honest with yourself here), add a 3rd. Nobody else is "blue chip", regardless of how much you like them.
No rebuilding team is getting 5+ 1sts in such a short period of time, unless one or two players hold the value of two 1sts on their own (in separate years). The more players on the market at once, the less likely you get full value. That's why it takes multiple years to rebuild.
You have to piece out your roster to match situations as they develop, where you will get maximum return as teams look to fill needs and address roster issues.