If a person of sound mind wishes to end their life, they should be able to. Forcing someone who is experiencing constant excruciating pain to endure that pain until the natural end of their life is cruel and inhumane.
Also, why would someone's academic qualifications entitle them to essentially sentence a suicidal person to death?
[1]: e.g "Also, if by some chance a psychiatrist doesn’t give a patient Adderall, that patient practically always goes to another psychiatrist, and that next psychiatrist does." (https://slatestarcodex.com/2017/12/28/adderall-risks-much-mo...)
Your argument goes both ways then, both for those who are pro-euthanasia and those who completely are against it.