I react so negatively to rolling for ability scores (and hit dice for the same reason) that its hard to even summarize.
Its like people who drive 45 miles per hour on a 65 mile per hour interstate, for no reason except that they feel like it. Their decisions affect other people in a small but negative way. They, for trivial reasons, have chosen to make other people's lives just a tiny bit worse. The sheer banality of it makes it a moral issue.
WOTC is choosing to make the lives of children worse for almost no reason. Adults who have been gaming for a while will know to choose the ability score generation system that they like the most. But having rolling for ability scores be the "core" method makes people say the game "feels like D&D," so rolling is listed as the primary method.
That means it will be the method used by new, younger players. They'll roll ability scores, invariably some characters will be way better than others due to these die rolls, and someone's first character, the one with a ridiculous name and corny abilities that they believe to be TOTALLY AWESOME because that's what you're like at age 12... will be an utter bust. Because of this. A child life will be, in a small but noticeable way, worse. Thanks.