They haven't really changed the whole strong heart requirement.
Most wielders we are aware of have undergone the Keyblade Inheritance Ceremony to be able to have the chance at wielding a Keyblade IF they have a strong heart. They aren't guaranteed one, but if their heart is strong they will be able to call upon one. (i.e. Terra, Aqua, Riku, Lea, Mickey pretty much every UX and DR character we are aware of, Kairi by accident)
Then we have people who have the power by circumstance like Roxas, Xion, Vanitas...Replica Riku I guess??? He holds Way to Dawn...They can wield because of their association with the person they were "born" from.
Then we have Sora who is the biggest anomaly. He took Riku's Keyblade because he snatched it out of Riku's heart lol but then eventually the Keyblade chooses him. Anybody is honestly capable of this, but it's not common. Nomura has stated that Sora is a normal boy with nothing distinctly unique about him. If anything, what makes Sora unique is that he is willing to go above and beyond to do what he can for his friends, which allows him to accomplish feats that few others have. Again, anybody CAN do these things, but Sora ACTUALLY does it while others don't.
Sora is not extraordinary, but he is special because he loves his friends so strongly which gives him so much strength.