This...."But it's often described as a guide to the afterlife, where ordinary people can achieve enlightenment through merely following some very simple instructions. For a person who craves quick and easy enlightenment, it's useless."
is a form of argument.
I find no one I know states that ordinary people may achieve enlightenment through simple instructions.
So yes....the self inspired answer is true...it would be useless for that purpose. But that is not the purpose.
There are varying means and methods described which may enable one to attain a enlightened state. There are also means and methods described in which one may effect a powah of not the highest sort and also methods to use when all else fails. For virtually all circumstance of dying one finds the methods applicable for best result.
Now if one wants a full enlightenment death may offer a opportunity for practice to enable such. We are naturally presented with our full array of awareness composite and origin upon death. If one utilizes meditational means to prepare oneself for death by experiencing a very similiar thing prior one may utilize the state of death for purpose of enlightenment. This generally by recognizing what happens to be what one is.
Nothing simple about that nor the preparation for that. It takes years upon years of engagement in highest yoga tantra to prepare for that, to replicate through meditational means the occurance of a after death experience.
Other means for others from the most accomplished to the least accomplished are described. Means for the most fortunate of death circumstances and the least fortunate.
All is a spiritual practice. One should just study and advance in the spiritual while as a living human..... absurd perposterous. Why would one want to do that? Restrict oneself suchly. I should practice fervently while human then upon dying...be running from imaginary demons of self inspired composite....why would I want to do that? Use both why not?
And for those not so inclined to the spiritual one may have a more favorable rebirth. As with Powah of the lesser sorts. Or just dying with the persons body on the right side to disincline to a lesser birth due to lesser of the gross emotions....all is useful. Or with a unsuspecting death like falling off a cliff...eject consciousness upward....and on and on. Means for every sort of person with all sorts of spiritual developement or nondevelopement.
We may utilize everything, sickness fear desire pain and death for spiritual purpose. Such is this provided with intent.
And for your listening pleasure....a flash from the past...
To balance it a bit