I don’t think any rational person argues that Facebook isn’t doing anything useful at all, lots of people value the connectivity and ability to share photos during lockdown.
Facebook has a good and bad side just like humans do. For example, if Facebook got rid of the ability to post news, it would be a much better place.
The questions are twofold: does Facebook do more good than bad? Could the good be accomplished without much of the bad? The answers to both questions are arguably bad for Facebook.
There are plenty. There is no mirror corporation doing exactly the same thing under a different name. But there is no mirror to Microsoft, Google, Apple or any other large tech corp. These are corporations backed by ironclad IP laws meaning nobody can every play on exactly the same field. For something like facebook, the competitor is all things not facebook. Every time you share a new story via SMS, you are competing with facebook. Every time you send a message via email rather than via facebook you are competing with facebook. And ever time you visit a store's own website rather than their facebook page, you deny facebook a tiny bit of the world. That is the serious competitor.
The competition for Facebook is owning the social graph as a means to fuel advertising profits. Google+ failed, sure. Instagram would have been eating Mark's lunch right now if he didn't buy them, and he knows it.
Imagine a world where Facebook didn’t buy WhatsApp and Instagram. So I think the better hypothetical is “imagine a world where Facebook didn’t leverage its existing dominance to preempt competitors”.
Oh, since I do not use Facebook or Instagramm and only occasionally whatsapp, I can very well imagine a world without that all.
Still, if enough people would be fed up with FB, their dominance would fade away. Well, afaik Telegram (and Signal) gained lots marketshare lateley, so lets see
https://friendi.ca is a serious competitor doing mostly the same things as Facebook. (Except it's a social media site first, instead of an ad network first.)
Or completely remove posts and keep only Messenger and Whatsapp. I've been using almost only Whatsapp and Telegram to share stuff with friends and groups of friends for a few years. If I want to read news I look for them either on Google News or on the very web sites that publish them, the ones I trust.
If Google and Facebook would block news on my country I wouldn't notice much.
Facebook has a good and bad side just like humans do. For example, if Facebook got rid of the ability to post news, it would be a much better place.