I think a large part of the issue is that if the bill is passed, it will gradually be watered down as the years go by - it’s currently being proposed for those who are terminally ill and expected to live less than 6 months.
When abortions were first “allowed” in the UK, they were only to be used if the pregnancy risked mental or physical dangers to the woman; now abortions are given pretty much on demand.
How long until euthanasia is given on demand, for any reason?