Don't know if I'd go that far. Mainly because TSL doesn't have the telling aroma of George Lucas scat that the prequels do.
I have to agree that none of these can be called plot holes when the plot hasn't been entirely told yet. It reminds me of people who get into political debates by saying, "Obama (or George W back when he was in office) is the worst president ever!" Well, setting aside the fact that you're ranking them as worse than, say, Harding who was inept, Buchanan who let the country fall apart, Pierce who was a clinically depressed alcholic, or Jackson who actively participated in genocide, they also haven't finished their term! Seriously, are you so partisan and filled with hate towards others that you can't even wait to declare a sitting president to be the most epic fail in the past two centuries? Really?
The story isn't finished. You might hate the story. You might think it's not King's Quest. You might think it's melodramatic and can never be fully brought together to a satisfactory conclusion. And you know what? Maybe you'll end up being right. But for now, none of this is a plot hole. It's impossible for an unfinished plot to have a hole in it.
Also, I just have to point out my favorite "plot hole" is the one regarding the enchanter tricking Edward out of the mirror that begins with "I presume that...". I think that answers your objection, dude! You can't just presume an important piece of information then call it a plot hole! I think it goes without saying but obviously Random Wizard Who Freezes You (that was his full name. I checked the KQ Companion. Really) wasn't a Black Cloak! That's like saying, "I presume that the kleptomaniac dwarf was a Black Cloak, so why didn't he just take the Mirror off of Graham instead of other random treasures?" Or, maybe the writers are going with the original KQ1 in which we were never told that Edward lost the treasures. In fact, we were never told Edward even had the treasures. Ed just hears about them and sends his most powerful knight to obtain them by any means necessary. Which is probably the most historically accurate medieval thing ever to be in King's Quest.