In my experience Amazon Japan still knows how to pack books correctly, but I haven't ordered from them since the start of COVID... they properly secure books to a bit of backing cardboard (with shrink-wrap and/or rubber bands, usually) and then mount the backing cardboard inside of the packing box so that the books don't slide around and get damaged. I'm sure it costs like an extra 50 cents per package to do this, but presumably their customers demand quality in other countries where Amazon doesn't have a de-facto monopoly.