Black Friday isn’t what it used to be. Here’s why.

Americans hit malls and big box stores, hoping to snag Black Friday deals in what could be a make-or-break moment for retailers, who already are bracing for a more subdued spending season.

And despite the day’s dwindling relevance — it’s morphed into a months-long sale pitch — merchants of all sizes are digging in.

In Dallas, shoppers lined up outside the LEGO store at the NorthPark Center mall before it opened. But one of the first people through the door was not there for Black Friday but for a new...