We have three boys, ages 14, 13 and 7. Our two older boys were finished with strollers by age 3 or 4. They went all day at Disney without a stroller no problem when they were 4 and 5 years old. We were able to go at their pace and didn't need strollers. But every child is different, and our youngest teaches us that every day!
Our youngest is seven years old and has a ton of energy - he's on swim team year-round and his engine runs far higher than either of his brothers. He just ran the Princess Half Marathon Weekend 5K - it was his 4th 5K, I think. He's one active child!!! But he has two teen brothers who are up to 3x his size and can walk fast. He also has an anxiety disorder and ADHD and sometimes needs the sensory break a stroller provides. So we end up renting one in the parks. It doesn't feel like a typical stroller, but gives him both a sensory break and helps him keep up with his older brothers. With his engine running so high, he can exhaust himself quickly, so the stroller rental works out well for him.
So I always say do what works for each individual child. And the Disney Parks strollers are great when kids are too old for a regular stroller, but might need a little extra support in the parks. We get the multi-day rental (discounted!) and just pick one up when we need it.