It doesn't matter if Michael and Laurie are related or not, he's still clearly after her in the original.

The blumhouse trilogy removing the sibling connection wasn't the problem. The problem was Michael not having a specific target at all, and instead killing nameless randows we don't know or care about on a whim.

We spend most of the original following Laurie as she's stalked and watched by Michael. It's obvious he has his sights set on her. If he didn't, he wouldn't have spent the whole day following her around town.

Why he's obsessed with Laurie in the original? Who knows. Debra Hill stated at one point it was due to Laurie resembling Judith. But that doesn't matter. What matters is we know who Michael's after, it doesn't matter why.

This heightens the tension because we know who's in active danger. And this is the problem with 2018. Laurie and Allyson are our main characters in the movie. And yet Michael couldn't care less about them.

There are multiple times Michael outright ignores them like they're not even there. That's not scary. Even during the third act, if they escaped that house, Michael probably wouldn't follow them, he doesn't care.

In the original, Michael relentlessly pursued Laurie. It didn't matter if she ran, hid or did anything. He kept coming after her.

In 2018, Michael had to be knocked out, and driven to Laurie's house against his will by the doctor. If not for him, Michael wouldn've kept wondering around aimlessly all night, and Laurie and Allyson would've been just fine.