You shouldn't replace Docker with a shell script but you should understand (at some level) how Docker works. Unfortunately this code is pretty dense so it would probably take a while to untangle it.
I see such suggestions here and there, but after quick redditing I've got impression podman brings more chores being rootless and daemonless. I couldn't justify usage of it for myself.
Had short discussion with couple of friends more familiar with podman vs docker, they highlighted the case when you need to give access to docker socket (say for building images) or for other needs to someone who is not in infrastructure admins (devops) team. As we know, having access to docker effectively meant root access on host, so such untrusted parties access implies severe risk of your host belongs to someone else now.
For such cases, when you cannot guarantee the one who operates docker is the root on host anyways, podman starts to make sense.
