Trivia: The film's production was quite troubled. A crewmember named Ricardo Cornelius was killed in a freak accident when he was crushed by a Humvee and a stuntwoman named Olivia Jackson was severely injured, with her face being "de-gloved" and sustaining may injuries and fractures which resulted in the loss of her right arm. Thankfully she survived and made a full recovery and the doctors were able to surgically mend her face and other injuries.
Trivia: The film was released in North America in January of 2017- nearly 15 years after the release of the original film, which came out in March of 2002. (Although the film was released in late 2016 in other select territories).
Trivia: While the film had the lowest domestic gross of the series ($26 million in comparison to the $40-$60 million each other film grossed), it was somewhat ironically also the highest grossing film of the franchise internationally, and as a result also ended up being the highest grossing film of the series worldwide, earning $312 million against a $40 million budget. It serves as a rare example of a film that is a flop in domestic markets while still technically being a resounding success.
Trivia: The release of this film pushed the series total worldwide gross over $1 billion, making the series one of the most financially successful sci-fi/horror movie franchises of all time, in addition to the highest grossing film series based on a video-game.
Trivia: Every previous film ended with a dramatic zoom-out starting with Alice that teased the events of the sequel that followed. Appropriately, "The Final Chapter" ends by doing the opposite - dramatically zooming into Alice and ending with an extreme closeup of her eye. This also bookends the series, as she was introduced in the first film with an extreme closeup of her eye opening.
Trivia: The Red Queen is played by child-actor Ever Anderson. Anderson is the daughter of star Milla Jovovich and director Paul W.S. Anderson, who are married.
Trivia: The film was originally meant to be filmed in 2013 and released in 2014. Filming had to be delayed due to star Milla Jovovich becoming pregnant and writer/director Paul W.S. Anderson (Jovovich's husband) opting to take time off to help raise the new baby before he started work on the script.
Trivia: The first film in the series has several allusions to "Alice's Adventures in Wonderland." As a nod to that, writer/director Paul W.S. Anderson subtle modeled the first creature Alice battles - a flying, dragon-like being - after the "Jabberwocky" from the sequel novel "Alice Through the Looking Glass."
Answer: In all honestly... this film series isn't one to shy away from ret-conning elements of prior films. ("Ret-con" being short for "retroactive continuity" - a storytelling device in which rules and plot-points are either changed or ignored in later installments.) This just seems to be another example of a ret-con. The idea that Alice was the "cure" all along would have ended the series a lot sooner, and they wanted to make more movies, so they just sort-of "ignored" this idea in the sequels that followed "Extinction."