Imagine a standard reasonable player raises UTG 6-max to 3bb
Folds to Hero on the Button with AJo or KQo

My standard here is to fold.

I haven't really questioned this, as it's something I started doing long ago, and just kinda have went with it for years.

When I do an equity calc, range vs range, it appears that it would be a profitable hand to flat call against a 15% ish range. Some players may even be opening a bit wider than this, including things like QJo, KJo, K9s, Q9s, J9s, etc.

So, is this really a correct standard? Is my "standard" incorrect? What would justify this as a standard fold? Is this just a remnant of something I did in the past when I was learning the game and less experienced?

It just appears to me that a hand like AJo or KQo likely has enough equity to play the button vs that kind of range, but I'm hesitant to just start cold calling these hands without questioning it.

A potential flaw I see in equity calculating, is given this idea, a hand like ATo appears to "have enough equity" in this same scenario. But I am much more confident that ATo is certainly a fold, even with it "appearing" to have significantly enough equity.

Where am I going wrong here? Where is my analysis incorrect? What would be a better way to look at these preflop situations?

Ryan