Is it considered an act of disobedience (ʿuqūq) and a sin for a son to abandon his father, who is ill with dementia, in Mecca after having traveled with him for Umrah?

Kindness and dutifulness to parents are obligatory, especially in their old age and when they are in need of care and attention. This is one of the best times to attain great reward. Allah Almighty has commanded kindness towards them and has forbidden saying "uff" or scolding them. He has commanded speaking to them with noble words, lowering the wing of humility to them, and supplicating for them. The Prophet, peace and blessings be upon him, warned that whoever reaches old age with their parents and does not enter Paradise. Patience is necessary with a parent's harm, especially if they are afflicted with dementia. As for leaving him in Makkah, it is permissible if there is someone who can care for him perfectly, along with visiting and checking on him. Otherwise, that is one of the greatest acts of disobedience, and repentance is required to rectify the matter.