It’s a really terrible way to go too. Lost a friend to it several years ago. At first there was some hope. Word was brain cancer tended to stay put, didn’t spread like cancers below the neck. They cut out the tumor, and chemo rounds were taken. Then they said she was cancer free.
But it came back, they operated again. Then came the seizures, which became more and more frequent until she finally died during one.
She was a fighter, but I have zero doubt given the option she would have opted for doctor assisted suicide that second time.
Not every terminal patient can pass through the doors of death in a perfect state of "pain-free, calm and alert." (THOUGH A LOT CAN -- A LOT MORE THAN WE REALIZE.) But everyone can go at least in a state of "no consciousness of pain, no seizures."
Excellent palliative care is,I would say, a right (and ought to be much more available.) Suicide is not. It's just part of the general crime of homicide.