Disagree on the point and reasoning about the single database.
Sounds like they experienced badly managed and badly constrained database. The described fks and relations: that's what the key constraints and other guard rails and cascades are for - so that you are able to manage a schema. That's exactly how you do it: add in new tables that reference old data.
I think the regret is actually not managing the database, and not so much about having a single database.
"database is used by everyone, it becomes cared for by no one". How about "database is used by everyone, it becomes cared for by everyone".
Sounds like they experienced badly managed and badly constrained database. The described fks and relations: that's what the key constraints and other guard rails and cascades are for - so that you are able to manage a schema. That's exactly how you do it: add in new tables that reference old data.
I think the regret is actually not managing the database, and not so much about having a single database.
"database is used by everyone, it becomes cared for by no one". How about "database is used by everyone, it becomes cared for by everyone".