Mass euthanasia - humane murder, or "medically-assisted suicide"; is already established in many nations, and will probably expand to become the statistically-normal cause of death.
The reasons are
1. That the ruling class want this to happen; and
2. That many people in The West want it - for themselves.
And they want this, because their fundamental understanding of human life - including their own lives - is that it is purposeless and meaningless. This conclusion (whether explicit of implicit) is almost inevitable when our society assumes (as well as argues) that there is no creator God - therefore no purpose generally or for individual persons; no spiritual world; and no possibility of existence beyond death.
Without meaning or purpose, life is merely a matter of current feelings - a balance between pleasure and suffering.
Many people live in fear of suffering; and because they are so afraid of future suffering and will do almost anything to avoid the unbounded possibility of sufferings; they have rendered themselves willing dupes to the machinations of evil.
Religious prohibitions against suicide have near-zero traction nowadays; because most Western people solidly believe (and our society assumes in all its functional systems) that death is followed by total annihilation.
For such people, the "problem" is therefore how to die without suffering; and this seems to require that they will be humanely-murdered by... someone else; ideally, killed just at the point when the prospect or actuality of severe and lasting suffering becomes probable.
People also believe (or, at least, behave as if they believe) that this point can be established, and suitable death-inflicting mechanisms decided, by a sufficiently rigorous bureaucratic procedure.
Against this there are explicit religious prohibitions - but hardly anyone nowadays takes religion seriously when its demands conflict with perceived personal interests or societal pressures.
Also against this is a deeply buried, inarticulate, usually uncommunicable gut-feeling of the wrongness of a world of bureaucratically-decided death - no matter how painless it might be.
Yet this feeling of wrongness, probably because it cannot be coherently expressed in the context of modern ideology, is too feeble to counteract the strength of social pressures when these are implemented in laws and procedures; and when endorsed by officialdom, mass media, celebrities, and peer group/ neighbours.
I therefore find it useless to argue against those many who advocate the introduction, spread or normalization of assisted suicide; because the arguments I can use all assume the atheist-materialist utilitarian world view - and thereby actually worsen the underlying spiritual problem.
The bottom line is that if you regard your life as purposeless and meaningless, then naturally it becomes merely a matter of subjective expediency how and when you die, or get killed.
When life has no meaning, death can have no meaning.
When life is a matter of being got-through as pleasantly as possible; then the same applies to death.
To tackle the real issue requires deepening the discussion to a metaphysical level, the level that addresses the ultimate nature of reality and our relationship with it.
Unless someone is prepared to have such a metaphysical discussion, then nothing substantive and positive can be done for them.
And this applies at the societal level, even more than at the individual level.
When people are trapped by their false bottom-line assumptions, then nothing helpful can be done that fails to confront the falsity of these assumptions.
And for that to happen, absolutely needs their cooperation in the process.