Could anyone expand on why they must build social products from scratch instead of adapting existing products? It seems to me, the existing problems they have

Could anyone expand on why they must build social products from scratch instead of adapting existing products? It seems to me, the existing problems they have with the upgraded products are simply usability design problems. Something that could be fixed by just moving the right elements to the right places. Or, more importantly, adding links to the right "methods" of the right products at the right places in other existing products. I do think they've been making terrible design decisions lately, but that seems like something that can be fixed by just... getting better designers and listening to feedback. Why exactly is that some people think otherwise?