It's always interesting to me when I see someone build a complete personal system around functionality that to me would just be a text file, or maybe an org-mode file.
For me it’s Notes.app, and I appreciate the notes being available offline and syncing across devices. Full text index is great.
I guess I’m lacking calendar invites, but I’ve been able to copy contents into AI to have it generate calendars for me.
I also don't keep dossiers on all my friends, so for me the entire premise is just academic.