With all due respect, this is why we have the problems we have today. Most people who spread COVID would say they truly believed they were not infected on the days they spread it. Sure, there are the idiots who test positive or have a close contact who they already know is positive, but they are outnumbered by the people who claim, "I did everything right, and I still got it." People are horrible at evaluating risk.
There will be lots of people walking around WDW (really, anywhere) thinking "everyone else is vaccinated, so I can be hesitant." Many of them will claim they just wanted to make sure the vaccine is safe, and are waiting a little longer. Deciding that people who make poor decisions "deserve whatever they get," is no more acceptable tomorrow as it is today. We have 5000 years of history of people make poor decisions, I don't know why people expect everyone to be perfect. We have to operate as if people are dumb, because we are. It's also clear people don't really understand herd immunity. It makes the fire harder to get started, but once it's started, it will still burn. Reaching 60-70%, whatever it is will make this phenomenally better, especially when it comes to hospital beds and staffing. But the other 30-40% will still be at risk, there will still be flare ups and still don't deserve to be harmed so that someone else can enjoy a vacation. Maybe, when it's like other infectious diseases at 95% the unvaccinated can be shamed. But again, so many health & safety rules are for protection of a small, vulnerable population while the greater masses will experience minor or non-existent outcomes. 40% compared to that, is still a lot.
Basically, this is not about you. You won't be asked to wear a mask because of what is in people's heads, but because too many people will still be unprotected, and it's hard to enforce, and often discriminatory to have different sets of rules for different people. Heck, that's why so many anti-restriction people are upset. Different rules for different groups. This is not going to go away overnight, and we're going to have rules to follow for months after non-medical minds think they are unnecessary. But it won't be forever. Just longer than people think.