[chousuke]

Honestly, I don't think that argument holds much water.

Init systems are not "just shell". If you go and try to write a sysv init script with only shell skills, chances are your init script will be broken in some obscure way. Perhaps because you didn't specify LSB headers correctly, or your PID file handling is subtly broken, or you're missing a check somewhere and the script is racey. I can't really say how much reading it would take to catch all the corner cases with sysv init scripts, but for simple cases, you will be able to write a correct unit file after about 15 minutes of reading the manuals.

Knowing shell helps, but you'll still need the tool-specific knowledge.