Looking back at draft-day deals that involved picks in say the top-20 for established NHL defensemen, the few that stand out for defensemen traded are:
2021 - Chicago trades Adam Boqvist (#8, 2018), #11, #43 and a protected 1st in 2022 or 2023 (#6, 2022) to Columbus for Seth Jones, #31 and #173. That was the price for what was considered to be a legit 1D, [The fact that he's sucked since going to Chicago is a different story.]
2021 - Vancouver trades Loui Eriksson, Jay Beagle, Antoine Roussel, #9, a 2nd in '22 and a 7th in '24 to Arizona for Oliver Ekman-Larson and Conor Garland. There was a huge cap dump in there which the Coyotes wanted, and on paper it looked like a possible steal for the Canucks, but Garland isn't much better if any and OEL has fallen off a cliff.
2021 - Philadelphia trades Robert Hagg, #13 and a 2nd in 2023 to Buffalo for Rasmus Ristolainen. Hagg was nothing - he later went to Florida for a 6th. Ristolainen, ... not sure you'd call him a 1D now. Or even a 1st-pairing guy, except on the Flyers.
2019 - NY Rangers trade #19 and Neal Pionk to Winnipeg for Jacob Trouba. Pionk in only his 2nd season in the league was 2nd on the Rangers blueline for ice time, so that's not an insignificant price.
2015 - Calgary trades #15, #45 and #52 to Boston for Dougie Hamilton. If you want to talk about acquisitions of a young, talented defenseman with 1D potential at the time, this is it.
So the idea that we'll get a 1D - even just a 1LHD who's really a 2 (which wouldn't fix anything IMO) - for the pick at 26, even with 1-2 picks in the 2nd attached, seems far-fetched. If you're going the trade route to fill that hole, it'll take the pick at 10 and then at least another pick. If another team isn't that keen on moving the guy we want, the asking price just goes up from there.
Which again, begs the questions: do we really think this roster as it stands is a 1LHD away from being in the top-4 in the West? If not, how much more tweaking has to occur to get us there - and at what point do you say "let's just rebuild and play for a few years out?" Not saying this roster can't get to top-4 in the West very shortly without a lot of work, but it's going to take significant rebounds across the board / guys making everyone excited after the last ~10 games continuing that next season for a full season, and you're talking about doing it with a defense where everyone outside of Rosen will be 30 at the start of '23-24 [Rosen will turn 30 in February] and the "youth ready to go" is Tyler Tucker [6/7 guy], Matthew Kessel [6/7 guy] and Scott Perunovich [Krug 2.0 and with a growing injury history].
IMO, that's asking a hell of a lot.