Maybe not in the US, or in your bubble, but a lot of people still use FB to connect with friends and family, or their groups of interest. Many more use it for the marketplace, to sell and buy things. For them FB is an indispensable venue.

As for helping divide society/ politics, have you paid attention to HN front page the last few days? Wave and wave of OpenAI posts, with huge amount of ignorant, uninformed, speculative, conspiracy driven, repetitive, divisive comments that got endlessly upvoted and promoted. That reflects who the HN audience is and what we are interested in. You may say that HN also helps divide society/politics. Yet you, and I, are still here.