We have Euthanasia in The Netherlands for decades but there hasn't been any evidence of abuse as far as I can tell.
There have been some cases where there was prosecution of doctors because of protocol violations.
But I can't recall any 'abuse' of killing of elderly people for the inheritance.
The reality is that nothing is fool-proof. In theory anything ever can be abused.
But the risk of harm vs. the risk of benefit is too great in favour of the benefit.
That's why we drive cars even though they kill 40K+ people a year in the USA.
So I don't think the theoretical risk of abuse is a good reason to not allow Euthanasia.
Edit: In The Netherlands, each case of Euthanasia / request for assisted suicide is evaluated by multiple doctors / psychiatrists. Each case has to be reported to a special Euthanasia commission that will also verify if things were done right. We don't go over it lightly.
That responsibility of doctors/psychiatrists to evaluate the case for allowing an individual's choice to die must weigh heavily at times. I remember the case from two years ago of a teenager who, because of an awful childhood, was mortally depressed and chose to die. UK news report [1].
In fact, in recent years a slippery slope has been entered, particularly with the decision of the Hoge Raad (21 April 2020) that euthanasia can be legal if a declaration has been made in writing, but the patient resists at the actual fulfilling of the request.
Also, political party D'66 is now pushing for the right for someone to end their life if they consider it "completed", without there being any serious suffering.
Note that not only the christian parties, but also the Socialist Party is very critical about broadening the criteria for euthanasia.
Even if someone with dementia is occasionally killed against their will (whatever that even means), this is an incredibly small price to pay to reduce the suffering of the people suffering from dementia who want to be euthanized.
I doubt they just created a law for this and just walked away. According to this [^1] news article made in 2019, of the 62000 cases of euthanasia there were 15 that might not have been what the patient wanted. In only 3 of those 15 it seems that the checks were not properly conducted.
There have been some cases where there was prosecution of doctors because of protocol violations.
But I can't recall any 'abuse' of killing of elderly people for the inheritance.
The reality is that nothing is fool-proof. In theory anything ever can be abused.
But the risk of harm vs. the risk of benefit is too great in favour of the benefit.
That's why we drive cars even though they kill 40K+ people a year in the USA.
So I don't think the theoretical risk of abuse is a good reason to not allow Euthanasia.
Edit: In The Netherlands, each case of Euthanasia / request for assisted suicide is evaluated by multiple doctors / psychiatrists. Each case has to be reported to a special Euthanasia commission that will also verify if things were done right. We don't go over it lightly.