First, regarding the idea of charging people to access websites:
This notion is a very Silicon Valley / coastal elite mentality IMO. A significant majority of people on the internet do not and will not pay for anything - largely because most people around the world just don't have the money for stuff like that.
The data on this is pretty consistent - take Netflix for example. A majority of Netflix users choose the cheaper ad supported tier, even though it is very easy and only marginally more expensive to switch to the non-ad supported tier. And this is already filtering to the subset of people who are willing and able to pay for a streaming subscription to begin with. The same case exists for Reddit -> you can pay to have ads removed, but only 1% of users do.
I see what you mean by Hacker News, but it's not a great example, since there are currently no ads and it's free. It's provided by Y Combinator, which monetizes via investing in startups (not something all internet businesses can reliably just start doing). For example - how would Reddit monetize? You cannot really expect people on Reddit all to be willing to pay to use it. And if some were - the whole value of a network is its scale -> so the drop in users would effectively kill the site. That's why there are no subscription only forums out there (at least none that I know of).
With regards to your second point of if these social media sites should even exist in the first place -> that's where you the consumer get to decide. If you don't get value from it, just don't use it. People who do get value from it -> use it. If enough people collectively decide it's not valuable, then the website becomes irrelevant (see Google+ and MySpace).
This is where I get very confused by anti ads people - show me a reliable alternative that is proven to work. Show me that people across the world, not just in San Francisco or London, can and will pay to access these websites/apps. And I'm not just talking about Meta - what about every random small website you have ever accessed that is ad supported? What about news websites like BBC? Or independent content creators who monetize via Instagram / YouTube ads? What about that wiki for that favorite video game of yours? Or that cooking blog? Don't get me wrong - I hate seeing ads as much as the next guy - but I can't really picture a realistic alternative.