A) Dermott is not a "marginal 3rd pairing defenseman". He's the best 3rd pairing defenseman in hockey, and clearly has more to offer.
B) I've read multiple times Dubas' choice was Aho, but Hunter wanted Dermott and we got Dermott because he was the final deciding factor. Andersson would have been a marginally better choice, but I'd take Dermott easily over any of Carlo, Cernak, and Hintz.
C) Hirvonen was a fine 2nd round choice, and just because you took one quote from a website where you're ignoring most and describing him (incorrectly) doesn't mean you have a case that he was a bad choice. It's too early to tell. Stop worrying about NHL players size, it's not 1960.
D) Stop bringing up the 2015 draft, it was a fine draft as we managed to hit on our high % picks (1st/2nd), but the excitement was solely due to a regime change where we stopped taking exclusively low-skill, decent-floor guys. Go back and look at the difference between 2008-2014 (Burke/Nonis) and 2015 outside the top-10. It was like a weight was lifted off most Leaf fans backs as some of these guys drafted outside the top-10 actually looked like they COULD be something. We were wrong, especially about Hunter (and lots of us could see it after 2016) but we took a step in the right direction. Since 2018 by virtually every model/prospect expert we've become easily a top-5 organization at drafting- but that's all speculation until about 3-5 years after a draft when you can actually see what these players will become. For now, you need to look at these players as assets, and see that almost every pick in the Dubas era has either kept their stock or improved it.