"poor experience" is subjective not objective.
Everyone who goes to theme parks at busy times knows there are going to be queues. They also know that fast passes are available and people are going to be using them.
If the queues don't make the experience good for someone, then simply don't go. Or go at a time when there are less queues.Or pay for a fast pass.
If fast passes were really creating a significantly poorer experience for non fast pass customers, then they wouldn't go. They clearly still do and turn up in multitudes (hence the queues), the only thing that is important to the business is that they do so.
You can hope for example that airlines will stop business class, because the idea to someone in economy that someone is travelling with more space, better food, service etc devalues their experience of their economy flight. But airlines aren't going to stop business class any more than theme parks are going to stop fast passes. While there is a market they will cater for it.
I respect people who vote with their feet, and respect people who are willing to accept the limitations of what they pay for/the value they are getting.
What I don't have much sympathy for are people who still go even though they feel the fast pass situation "ruins" their experience. If it is that bad then don't go.
I think there is probably an argument that the actual wait time increase caused by the fast passes on the non fast pass customers is probably pretty negligible anyway (the number without fast passes completely dominates over the fast pass holders). But I don't have any stats on that.
It does seem a bit weird to me how they make the fast pass holders walk pass the entire queue to get people onto the ride. I would design the rides with shorter access for the fast pass from a different area, or maybe a tunnel they could walk through. That would probably cost more though.