I agree with the author that the various levels of isolation, etc. within the current crop of SQL databases is a morass. I’ll point to some recent fine work by Martin Kleppmann (https://github.com/ept/hermitage) that explores the issue and shows how many systems fall short of serializable isolation in their default modes. (And sometimes in modes labeled “serializable”!) In his test three databases actually achieve full serializability: PostgreSQL, MS SQL Server, and FoundationDB.
But don’t give up on ACID yet! If can actually get real serializability, you have a very powerful model that is also very simple to reason about. Serializable isolation gives you a virtual “whole database lock” that lets you modify lots of things all over the database before you “unlock” it and hand the database to the next client. The amazing thing about MVCC combined with serializable isolation is that you get to use this "simplest possible" mental model even though hundreds or thousands of concurrent clients might be all hitting the database at the same time.
But don’t give up on ACID yet! If can actually get real serializability, you have a very powerful model that is also very simple to reason about. Serializable isolation gives you a virtual “whole database lock” that lets you modify lots of things all over the database before you “unlock” it and hand the database to the next client. The amazing thing about MVCC combined with serializable isolation is that you get to use this "simplest possible" mental model even though hundreds or thousands of concurrent clients might be all hitting the database at the same time.