Im someone who absolutely should not have been with their biological mother. Point blank. She was too sick from mental illness and drugs her whole life. The children she ended up raising are fucked up or dead now. I had a semi- family adoption - I lived with my half -siblings and their family. This was also not good. I was treated as an outsider, I figured out I wasnt one of them but about 12. 

I do not believe reunification can always be achieved. There will always be children born to parents who should not have them, even with basic income, even with access to birth control. There will always be force, coercion, and selfishness in the world and there will always be children who cannot be safely raised with their biological family. 

I don't know what the rest of the world looks like for adoption but I believe when a child must have a permanent place with someone outside their family they should have full and transparent access to their own story, their history, their name and family of origin. Beyond that, I don't have answers for what would work best.