Like Bitcoin, it doesn't impose itself to fix things actively; it's a protocol, after all. Those who embrace it, take responsibility for their use of it, and step away from the incumbents will benefit.
Discussion
Mastadon and Peertube happen to use protocols that don't actively push balkanization but the design clearly incentivizes it, regardless of original intent. Mastadon is quite upset Gab is the biggest node, I hear.
Im not saying Nostr is bad or doesnt have any benefits, quite the contrary as it has quite a lot, but I'm unsure it could do anything but make this specific phenomenon worse. Its design creates financial incentives in basic social interactions. Look at how the "like" system has altered peoples behaviours and outwardly spoken beliefs then imagine if they could pay their bills with those likes.
It could also make audience capture more pronounced as well, but only time will tell for most of these things.
Obviously, I wouldnt be here if I didnt support it over everything else but, like with Bitcoin, we must be aware of the tradeoffs for informed use.