WOSF Episode 38
Adoration turned out to be the most important factor.
Because it IS the most important factor!
I try not to be resentful of the fact that I wasn't taught much about it earlier and was in fact actively discouraged by my RCIA teacher (back in my day, we spelled our acronyms differently!) because he felt that converts should be discouraged from taking up practices that were "too Catholic" because it would prevent us from evangelizing other Protestants. So my questions about things like Adoration, the Real Presence, the Rosary, scapulars, novenas, etc were all dismissed and I was actually warned against exploring them.
It left me with the unfortunate impression that the reason for closed Communion was no different than what my father had told me about our closed Communion in the Anglican church when I was a child - keeping out the riff raff. Like a private club membership. And I was just getting my Catholic membership card so I could have history and beautiful art and architecture and get to attend a liturgy not a rock concert on Sunday mornings, while also being in a church that was solidly pro-life unlike the modern Anglican church. The reason my teacher gave for why the Catholic Church was true and better was merely "apostolic succession", which is nice, but it's not the actual reason, and it's not really going to convince many Protestants either.