An init system is for all practical purposes a build system - a very complex problem where literally every sane solution is declarative. Especially when you take into account error handling (that HDD is not yet available, will you imperatively wait for it to come up and pause everything else? Do parallel work in the meantime in fking bash? Or what exactly?)
Startup is ultimately a complex problem. There is no magic, just race conditions which maybe became more apparent. LVM may or may not be used, and takes time to start up. Do you wait for it? Ditto wireless networks. And how do you handle devices being hotplugged? Setups vary widely, and can be dynamic.
