I'm 100% agree with you, I think this relation is one of the strongest element of the comics, I think the Chinese audience could be open about that but that could be more complicate with the censorship.

Now, if Shang Chi is more or less his adoptive son that could work, the leak describe him like a beggar, so he probably admire the Mandarin deeply to have saved him and to have given him his chance, sure it's probably less intense and less intimate that to be his blood relative, but that could work.

Now I hope Marvel change their minds, the closest to the comics, the better for this aspect of the story imho.