I agree with this. I didn't even think that the Izek/Ireena thing was all that contrived personally.
The Izek/Irena thing also talks about Izek "coveting her in an unwholesome way" which is a pretty standard trope in modern horror movies and stories, from Dean Koontz novels to Halloween (though Michael, just wanted to kill Laurie it's still dark urges toward a sibling).
Compare "Prevent creepy and psychopathic fiendish brother from abducting sister to quench unholy and unnatural urges" to "Prevent ancient undead monster snatching reincarnation of centuries old object of obsession to make his undead bride", and you've got a microcosmic reinforcement of one of the key adventure themes. That both happen to be focused on the same victim may put too much spotlight on Ireena, but could also make for some great roleplay opportunities if Izek's got the Burgomaster and town guards as allies. The players may need to make a deal with Strahd or his allies in order to protect her.
I'm planning on offering opportunities to embroil my players' group in the Vallaki subplots as early as possible. However, I think the strongest of the Vallaki story arcs is the plot by Lady Wachter to overthrow the Burgomaster. This can almost force them t o choose sides in this one, but good luck finding the "good guys". That there likely isn't one means the group themselves could become one, or go the US in Iraq route, cutting off both heads, and leave the town without a direct ruling faction so that Strahd steps in personally. Sometimes, "freedom from oppression" leads to worse oppression by someone else. (Strahd, or Lady Wachter's infernal cult, should they gain power)
Heck, that might be exactly what Strahd wants. First, to see if any of the characters are capable of stepping up and filling a leader's role in this land (the whole "worthy successor" thing), or simply to remove any opposition to his preferred method of governance. Once all the guards and cultists are done killing each other off, wolves and dire wolves start roaming the streets of the village, and nightly attacks by intelligent undead become the norm. Vallaki would resemble Barovia village over time with no one going outside, ever. Characters with good intentions would see clear evidence that their interference made life for these people worse, another stepping-stone toward despair, yet another kind of horror.