I'd agree with this completely. Some people look at the behemoth that is Walt Disney World and think: there's so much I want to do here and I gotta do it all! Of course, WDW is enormous. You could go again and again and not cover everything. But for some people, the sheer volume of must-see and must-do activities is overwhelming. It's understandable why so many people have the need to plan out every detail. But when people ask me whether it's important to have a detailed plan, I say there's no right answer.
FWIW, I showed up my first time at WDW, and bought a 3-day ticket at TTC (not even in advance!). The CM asked me if I was going to Epcot for F&W, and I had no idea what that was. She said, "oh go check it out!" With zero plan, I hopped on the monorail to Epcot and had a great time. The next day, I went to AK in the morning and MK in the afternoon. Just going with the flow. Hakuna matata. With some planning, I could've checked off more things from a list but I don't think I would've necessarily gotten more "value" out of my vacation, if you define a vacation value as being incredibly relaxed and happy, and just enjoying yourself. I've seen people get so stressed out about their plans that I've thought they most certainly aren't getting their money's worth... but who am I to say that it's incorrect when they value things differently?