I understand the preconceived notion idea, but sometimes it doesn't work even if they go along with a trip with more planning. Many years ago (before FP+), I "planned" a trip with 2 family members to WDW. I didn't book ADRs, there was no pre-booking fastpasses and we picked our park each morning and our rides as we walked to them. Their only complaint was when we couldn't get ADRs day of because I hadn't known they had to be booked in advance.
Fast forward to last year. I planned a first trip for DH, my kids, and I and those 2 family members tagged along. I tried to explain how things were different and required more planning and tried to get their input on fastpasses, plans, restaurants, etc, but they said they'd just go along with whatever I planned.
The trip comes and they complained about every bit of the stuff I'd planned. Why do we have to go on this ride now, can't you push back our ADR, why'd you pick the hottest day to go to this park instead of a water park, why can't we just wing it like we did before? I tried explaining how much work went into the planning, about losing money in cancellation fees if we missed ADRs, pointed out the standby times of 60+ mins, and explained that I had done my best to plan things for 6 different people all with different interests with ZERO input and that they were welcome to go off alone if they wanted to. It didn't matter. They basically wanted a re-play of the previous trip, except with better food, but couldn't understand why that was no longer realistic or why I didn't want to go from ride to ride and wait in 45-60 min standby lines with a toddler for POC or iasw, nor did they want to split up. Basically, nothing could be done at that point to make them happy without forgoing all the planning I had done to make the trip easier for my own nuclear family.
I've realized that often people have an idea of how a vacation will go and if it doesn't happen that way, they are not willing to accept the changes. That happens on both sides. They didn't want to have everything planned out and lose the spontaneity. I didn't want to not have ADRs or miss them and pay canx fees, and didn't want to wait in long standby lines.
Sometimes planning a trip for people with different touring expectations doesn't turn out the way you'd like.