Blue
Ravenous Bugblatter Beast of Traal
It's just a matter of perspective. It's not something you can argue as logically invalid.
You are incorrect. This is not subjective, it IS possible to care about more than one thing and have one having a higher priority then the others.
Personally, I will say that if you don't care enough to optimize your AC for your character class, then from my perspective, you don't really care about AC. If you tell me that you care about AC, but that you care about your spellcasting more than you care about your AC, then that's saying to me that you don't really care about your AC.
Now this is subjective. And also easily disproved.
With a +3 DEX mod, my valor bard could easily have kept the studded leather I was wearing when I hit 3rd and got medium armor proficiency. And kept their AC of 15. But instead I spent a good chunk (750gp!) of my character's limited gold to get Half Plate for AC 17.
Shown: I care about AC, I want it higher and am willing to spend limited resources on it.
Previously shown: I was using my ASIs to advance CHR, so I can care about something else as a higher priority.
Conclusion: It is very possible to care about AC without caring about it first.
Your attempts to say that if it's not #1 then it's nothing are not supported by logic. Or common sense.