So it's perfection or nothing? Occasionally I am getting as close to thinking as my character as is practical, so similar to when I'm really engrossed in a book for example. Is it perfect? Do I get to the point of actually believing I am my character? Of course not. But when I'm really into playing a character I sometimes surprise myself a little bit by what I say but it's also exactly how my character would react.
You seem to be belittling other peoples preferences and experiences because they aren't good enough to meet a bar set so high that only a small percentage of actors could ever achieve. But I think I also disagree your criteria. If a method actor is speaking lines from a script they may be feeling the emotions, riffing off how they think the character would feel while saying those lines but they're still quoting words someone else wrote. They have a version of that persona in their heads but they aren't creating the persona, they're implementing a persona. With improv you both inhabit the character and create them as you go along.
Of course I don't forget I'm playing a character, I'm not delusional. But I'm also not thinking "What would Klank say", I'm responding as Klank, at least some of the time. That's good enough for me.
