I agree, you shouldn't completly cut off your child, and still hold out hope for them to return and treat them well and advice them for their own best interest.
Keeping good relations with your kin is very important in Islam:
Aisha reported: The Messenger of Allah, peace and blessings be upon him, said, “The bond of family is suspended from the Throne and it says: Whoever upholds me, Allah will uphold him. Whoever severs me, Allah will sever him.”
Source: Ṣaḥīḥ al-Bukhārī 5643, Ṣaḥīḥ Muslim 2555
And the Prophet (peace be upon him) didn't sever ties with his family even though they weren't Muslim:
‘Amr ibn al-‘As reported: The Prophet, peace and blessings be upon him, said, “Verily, the relatives of my father are not my allies. Verily, only Allah and the righteous believers are my allies. Yet, they have the bonds of kinship and I will uphold their family ties.”
Source: Ṣaḥīḥ al-Bukhārī 5644, Ṣaḥīḥ Muslim 215
To your point about the Christians and Jews in the west that don't really adhere to their religion, I do think that's true. However, the are Christians and Jews that don't get upset about their children abandoning their religion, as you said, are the ones that aren't that devout themselves like in western, developed nations. In very religious Christian regions ike in places like Africa, parts of the Middle-East, parts of Latin America, for example, your family will cut off ties with you if you reject Christ and abandon their faith. So, I don't think it's fair to say "Muslims get angry when their children leave Islam, but Christians and Jews don't"
Christians and Jews do, for the most part, but the ones that you are attributing leniency to, I would argue, are mostly the Western Christians and Jews that already symbolically practice that don't get upset.
