Honestly, I thought JL was good. It wasn't great but it definitely isn't as bad as the critics made it out to be. It's definitely not the best DCEU movie IMO but it's a vast improvement over BvS and Suicide Squad.
That being said, the movie is opening domestically to around $96m which is pretty shocking and disappointing seeing as this is DC/WBs prime property. Not to mention apart from Logan it's the lowest opening superhero movie of the year. WB won't lose money on this but the optics aren't good.
The only things I can think of that could hurt the movie's opening weekend so badly are:
1. BvS. I know the movie has some hardline fans but it's obvious that a LOT of people hated that movie and this is ostensibly the last part of Snyder's trilogy. The movie's marketing made it look more like BvS than Wonder Woman and the folks that hated that movie probably didn't show up for this.
2. The aforementioned reviews. Although tracking wasn't too high in the first instance (it was tracking to open around $110-$130 million) I think the mixed to negative reviews drove away the casual audience.
3. Wonder Woman fans didn't show up apparently. WW was a cultural phenomenon with a large female audience and apparently a lot of them are not interested in shared universes.
4. The absence of Superman in the marketing. No matter how folks want to spin it, Superman is still the most recognizable superhero in the world, he should have appeared in the marketing. I know fans hate spoilers but when dealing with a property that MUST have crossover appeal, one has to consider the non-geek audience and give them priority.