So... how do Koreans and Korean learners do it? Not to mention other languages that used to use Kanji but dropped it?
You have to imagine the entire education system and everyone in it got changed to Kana only and Kanji was subsequently removed from modern literature from that point onward. That's the thought experiment. It was even tried successfully in places...
I don't know anything about Korean. It's a different language, and I'd imagine that some of the things I'm saying here don't apply to it, but that's a guess.
For thought experiments, you're assuming your consequent - obviously a society raised without kanji would get by without kanji, though I think the language would have to change somewhat. But for non-hypothetical people that exist now, I think the things you've been saying about kanji not making it easier to read Japanese just aren't true.
You have to imagine the entire education system and everyone in it got changed to Kana only and Kanji was subsequently removed from modern literature from that point onward. That's the thought experiment. It was even tried successfully in places...