And the point is, it's a burden you can't avoid, and never could

The magical fairy god mother file system that handles everyting for you doesn't exist, and never did.

If you want database like data integrity, use a database, and take the performance hit.

[...] do what application developers actually want. fsync here asks for something entirely different and imposes a stupefying performance penalty.

Do you realise that what you want is equivalent to having the FS do the fsync for you? If it is "stupefyingly slow" when you do the fsync, why should the fsync that the FS does be any faster?