That isn't actually a flip. It's part of the core assumption of what I wrote and was included fully in my reasoning when I wrote it. It still falls under the area of ignorance, in as much as a little knowledge is a dangerous thing, especially when it makes you think you now know better.
Having extensive understanding of the design philosophy and mechanics and years of playing D&D and other systems to understand the strengths and weakness of subsystems is not ignorance.
The problem with your post and why it might be wanting.
1. You can like D&D as a whole and not like some of the subsystems or their applications.
2. Ignorance: yes, if people don't have an understanding behind the philosophy and mechanics of Vancian, yes there may be ignorance. If people understand them and still dislike it and want something else, that is not ignorance. There may be ignorance about the drawbacks of implementing another system if they don't have the proper experience, but they may not be ignorant of the benefits it would bring.
And as I stated above, some people do have the understanding of everything involved and, for them, they are not ignorant on the subject.
3. Confusion. Many people understand Vancian and don't like it. For many of those that do not have an understanding, they still don't like the mechanic. after having it explained
4. High Simulation: Many players do not know the origin of Vancian magic. For many that do, they have not read the books, but know from boards and other sources that it is not truly Vancian just takes cues. So, there is no confusion.
For many , it just does not does not work for them. It is not a matter of having magic built from the ground up to match a particular setting that they saw in a book or movie. It is just a matter of wanting something closer to how they think magic should work based upon a collection of sources. It might also not wanting to have to not deal with long lists of spells in books.
To claim this is not a valid reason is dismissive.
5. Power gaming
a. No armor, slow casting, disruptable is not even about Vancian magic. It is how wizards and sorcerers were often portrayed in many sources that inspired D&D. Dislike does not, necessarily, have to be power gaming. For some people, the dislike may go to the source material with which they are familiar (I, personally, like no armor, slow casting, and disruptable).
b. dislike for pre-choosing and "fire and forget" is not necessarily about power gaming. It, probably, has more to do with going back to the source material with which people are familiar, consciously or unconsciously, and feeling a disconnect as you noted. It is however, wrong to assume it is a power-gaming issue or desire for spotlight.
Many people that don't like the pre-selecting or "forgetting" aspects, would be happy with a system that allows them to continually use the powers they know, but kept their power level in check with everyone else. They might also be happy with a system of fatigue or spontaneous casting (as per the sorcerer or the Unearthed Arcana variant: Spontaneous divine casting).
6. yep, that's common reason
Maybe, I misread your initial post, but it does read like you are too self concious of your own preference and others not liking it as you stated. Individuals don't have to be powergamers, confused, or be ignorant of D&D, Vancian and the drawbacks of other systems to dislike Vancian and want something. Their dislike for Vancian also does not need to indicate a dislike for the game as a whole- just one piece which some people think defines D&D and others do not .
In the end, we are just dealing with subjective preference and I think the designers have their hands full.