Looking at 1994 film Interview with a Vampire, why have vampires changed?.
Based upon your question, and the reference to Neil Jordan's filmatic adaptation (1994) of Anne Rice's novel (1976), I believe that your question is referring how (or why) the characterization of vampires have changed over time.
Rice's novel, and Jordan's adaptation, offer a very distinctive characterization of what vampires were. In Interview with a Vampire, Lestat and Louis were very different. Lestat was depicted by his thirst for blood, regardless of its cost on humanity. Louis, on the other hand, sympathized and empathized with humanity. His thirst for blood was appeased by his dining on animals.
Today, vampires are not depicted much differently. For example, in the newly restored appreciation for vampires (as brought forth through the widely popular Twilight series, both types of vampires are similarliy depicted.
Edward and the Cullens chose to feed their thirst by draining the blood from animals (given their attachment to humanity), while Laurent, Victoria, and James are all portrayed in the light of the typical vampire (feeding on human blood).
If one were to examine the casting of both Interview and Twilight, one would not see many differences between the physical characterizations. The vampires are strong, attractive, and have an air of superiority.
That being said, the vampires of today have changed in regards to their "acceptance" by society. It seems that the popularity of the new vampire texts have created such a craze that being a vampire is seen as "cool." Teenagers flock to the premieres, dress in clothing depicting their love of them, and (some) dream of being loved by one.
Prior to both Interview and Twilight, vampires were seen as creatures who preyed on humanity and were beings mankind abhorred. In that sense, the image of vampires has changed dramatically. Prior to one of the most famous novels, Dracula (1897 by Bram Stoker), John Polidori's The Vampyre (1819) provided a horrific tale of the menacing and deadly vampire. Both Stoker's and Polidori's vampires were a far cry from the modern Lestat or Edward.
Therefore in the end, vampires have changed the most dramatically based upon the fact that they are now being romanticised. No longer the creature of the night to be feared, the modern vampire would be openly welcomed if found standing at one's bedside.