Yes, that’s correct, but we have been used to thinking that way for a decade. I don’t remember how painful it was in the first place, but once you think in that way, things fall in place.
Any good resources you can recommend that would show me “the beaten path” for e.g. a todo list where users can selectively share items, or join teams - just a step or two more than the usual “every user gets their own data only”.