That's completely nonsense.
Claiming the earlier games were "judiciously presented" as an excuse for them being scant
It isn't an excuse. If it was, almost every Castlevania game would have a considerable number of excuses to make.

The plot elements in most Castlevania titles were indeed scant, but they always
sufficed. They managed to build a simple, acceptable story that always proved perfectly adequate in driving the game forward. And that was all that ever mattered; Castlevania never needed an overabundant plot or a groundbreaking narrative, since plot and narrative were never considered priorities. CV titles excelled in other areas, so developers judiciously went for
brevity and
simplicity, in a way they knew would not prejudice the game itself.
Now, would Castlevania be any better off with a deeper, more compelling story? Probably. Lords of Shadow pulled it off magnificently, and I wouldn't enjoy the title nearly as much were that aspect to dissapear. But the fact is that Castlevania never really "suffered" from its absence.
(...) while at the same time claiming that MoF did nothing to establish Simon's (or any character's) personality is silly. Alucard in SotN is somehow more developed than Alucard in MoF, despite the fact that all we really learn from SotN is that Alucard is a half-vampire who favors his human side and will fight his father despite their blood relationship?
Let's take a look.
In Mirror of Fate, Trevor is a man who wishes revenge upon his father for the murder of his mother. He journeys to Dracula's castle, travels through the castle, uttering a few dramatic platitudes on the way, fights his father, but gets killed. He is resurrected as Alucard, shouts nonsense about his fate, gets even angrier at Dracula, tries to kill him again, and this time succeeds by teaming up with Simon. THE END.
In Mirror of Fate, Simon, raised from boyhood in the forest, wishes revenge upon Dracula for the murder of his parents. He journeys to Dracula's castle, travels through the castle, participates in a few incomprehensible exchanges, and kills Dracula by teaming up with Alucard. THE END.
In Mirror of Fate, Dracula is the evil lord of the castle Simon and Trevor explore. When Trevor arrives into his throne room, claiming vengeance for his mother, he remains cynical, and they begin to fight. When Trevor is killed, he reveals that he is Dracula's son, upon which Dracula dramatically regrets his actions, and, grief-stricken, attempts to revive his son. Several years later, however, when Simon faces Dracula, the latter jumps at his own grandson and tries to kill him, yelling "I cannot suffer to see this bloodline live on any longer!" Fortunately, he is defeated as Simon and Alucard join forces. THE END.
So... how exactly does this consist of any better characterization than that offered in SoTN?
And there's not "scores" of cutscenes in MoF. There's maybe six per character, all together equaling 22 minutes in a 9 hour game (That's 4%), and individually they're pretty brief, with very few lines actually said outside of a select few.
You're right; there aren't "scores" of cutscenes in MoF. It's a poor choice of a word. Essentially, I'd meant that many cutscenes felt entirely unnecessary.
EDIT:
castlevania aria of sorrow - cutscene dracula reborn
I mean, this isn't exactly wonderful writing.
It's not wonderful writing, but it isn't terrible, either. For a GBA Castlevania game, it's actually rather good.
Essentially, here's my point: Mirror of Fate's plot, in itself, isn't really any worse than any other title's. But it so heavily burdened with convoluted dialogue, unnecessarily dramatic staging, and confusing narrative structures that it ends up tripping over itself. Yet it's still presented as if its story was truly supposed to be taken seriously -- something which, judging from the current state of its plot, is rather hard to swallow.