In earlier versions we had gnome and orca screenreader installed, so that live iso was accessible for blind users.
now I downloaded latest iso and saw that there is no orca installed.

I don't know what desktop environment is used by you now.
may be orca is part of gnome ecosystem in your package, so it was removed when you changed de of your iso.
please install gnome-orca package with deps to your iso.
also please check that:
speech-dispatcher package is installed
pulseaudio is set up to work in your root only environment
espeak (or espeak-ng if exists) is installed, but should be installed automaticly with orca