By staying true to the original book's story elements, I Am Legend 2 could risk ruining the Darkseekers. Unlike Richard Matheson's I Am Legend book, the original movie followed a tried-and-tested narrative, where Will Smith's Dr. Neville helmed the responsibility to save the world from a deadly pandemic. Despite having several predictable elements, I Am Legend appealed to the masses because of its slam-bang action scenes, desolate depiction of an otherwise bustling New York City, and Will Smith's brilliant performance.
https://screenrant.com/i-am-legend-2-book-darkseekers-vampires-weaker/