…ndjson is streamable, too…

I like ndjson and jsonl just fine, but unless I need a more complicated structure, it's not worth the extra hassle of parsing JSON.

… what concrete language are we talking about, here?

In literally any language I can think of, hassle(json) < hassle(CSV), esp. since CSV received is usually "CSV, but I've screwed it up in a specific, annoying way"

I'm thinking mostly of the computational complexity.

But even ergonomically, in python, can read a csv like:

  import csv
  [row for row in csv.DictReader(f)]

which imo is not less ergonomic than

  import json
  [json.loads(line) for line in f]