Our rule was always no strollers. So our kids didn't go until they were 5. That was a birthday gift from the grandparents who took them. My daughter went without us, my twins we went to help since my parents were a bit older and twin boys are different than a single girl!
We spent the entire 4th year of their lives working up to it. It became a huge theme. Start with small walks around the neighborhood, then hikes, trips to the mall, then zoo trips, etc. By the middle of their 4th year, it was a point of pride not to need a stroller for the kids and by the time that 5th birthday trip rolled around we hadn't used the strollers in a couple months and the kids had forgotten all about them. In addition, we started them mid year with small back packs. Then added a water bottle and some snacks to it, eventually a roll of quarters and pennies for the machines. Those packs were 5 lbs or a bit more, and the kids trucked them around all day at the parks.
We are fortunate that none of our three are special needs, so I understand this doesn't work for everyone. It also worked because we didn't try to bring sub-5 with 5s, so it definitely limited Disney for a few years. But it certainly is one strategy that I recommend when people ask. Not having a stroller at Disney is fantastic. Stroller parking, buses, crowded walkways, narrow shops, and now the Skyliner for doubles... uggh. No thanks... but more power to those of you that manage it!