What is the other extended familiy model? family clans? What would be the practical difference? Are the no disadvantages?
Exactly these political issues, which I have no strong opinion on, are randomly added to issues of police violence that makes the whole movement look very dishonest.
Where in the western world are people that tell you how to structure your family?
The movement isn't dishonest. Its critics are simply ignorant. That's not surprising; they've been kept in ignorance deliberately.
Yes, the suburban happy family living the American dream might be a touch too idealistic, harsh building regulation might drive prices which disadvantages poor demographics and there were maybe people that used it for racist purposes. Doesn't mean everyone did. And high density housing is probably a lot more stressful even without a family apart from the most expensive options available.
There is a long case history involving these ordinances, including extensive documentary evidence that occupancy caps and definitions of "immediate family" were designed specifically to exclude blacks (in the first half of the 20th century) and latinos as well (in the second), taking advantage of both the fact that black and latino households are far more likely to include grandparents, aunts, and uncles, and also the (obvious, in retrospect) fact that municipalities simply don't enforce these regulations against white households --- again, a fact documented in the case history.
At any rate, the dispute upthread suggested that there was no racial justice aspect to the "Western-prescribed nuclear family", and whether you agree with the courts or not, there clearly is such an aspect; the allegation that BLM is exceeding its charter by railing against "nuclear families" is easily refuted, and we should have all known better than to raise this objection in the first place.