The Meridith character is none of the things she is accused of by her father. In fact, she's just the opposite. Far from being a "slut," she clearly wants a loving, monogamous relationship with a decent man. However, she is imprisoned by the confines of her history of dysfunction. Meridith can only dream of the reality she so craves. The only thing left to her is memories of what might have been. This is a wake-up call to any real Meridiths out there. If you have unloving or abusive parents or partners, what they think of you should not be taken as gospel. There is a whole world out there, filled with many people capable of seeing what you have to offer and what makes you special.
As for the excess of negative reviews, they are in no way a fair criticism of the acting or the directing. In the latter case, young Thommy Hutson brings a complex, multi-layered story to life. He packs with it with stark symbolism that makes the story itself even more vivid and compelling. So, in a nutshell, the acting, directing, and writing are nothing short of superb. The problem is that there are so many people who recoil from staring down that rabbit hole that is their own past. Instead of engaging in thoughtful self-examination, they lash out with a negative review. When we're watching "Nightmare on Elm Street," we can walk away protected by the assurance that Freddy Krueger doesn't exist. That's not so easy with "The Id." Both the character of Meridith and of her father are people so many of us can relate to. Some such viewers aren't ready for that sort of exploration, but that's okay. What's not okay is to misdirect your feelings into an unfair written critique.
For reviewers of any kind of performance art, I encourage them to confine their remarks to correspond with the genre on which said art is based. For instance, I dislike most horror movies. When I saw "The Exorcist" years ago, it scared the pants off me, and I didn't enjoy the experience. However, within the horror genre, I had to admit that it was a classic. To call "The Exorcist" a lousy movie would have been grossly inaccurate.
In closing, "The Id" is not a movie that fits a night of mindless decompression after a hard day's work. If that's what you're looking for, pop open a beer and rent "The Naked Gun" or "Scream." But if you want an emotionally evocative experience that will stay with you and make you think, I can't think of a better option than "The Id." I would call this movie a "psychological thriller/tragedy" in lieu of categorizing it as horror. The occult makes no appearance in this film; it's all about what is swimming around in poor Meridith's head. So, be brave and watch this movie. After your more visceral feelings go away, you will find that it was both enlightening and gripping.