> Making data "non-relational" is not a cure for the above.
ACID imposes a limitation on scalability, there is no way to escape that. If you want to claim that approximately nobody reaches that scale, that's true, and if you want to claim that you don't need to ditch your data schema, that's also true. But relations aren't worth much without global coherence, and global coherence requires ACID, and will only work up to some size (that fits almost everyone, but not literally everyone).
But is tangential to be relational. You can have relational data in a causal way. Now, i see that some think "relations" are PK/FKs and that only GLOBAL coherence is the only way to make relations to work.
If we can take a JSON and make it valid and correct only in this replica in this moment of time, relational data can too.
ACID imposes a limitation on scalability, there is no way to escape that. If you want to claim that approximately nobody reaches that scale, that's true, and if you want to claim that you don't need to ditch your data schema, that's also true. But relations aren't worth much without global coherence, and global coherence requires ACID, and will only work up to some size (that fits almost everyone, but not literally everyone).