No social media was created to manipulate people. (Most) social media is a business, optimised to make money. You make money by showing people ads. You can show more ads to people if they stay on the platform longer. You can make people stay longer by engaging them emotionally. End of conspiracy...

But it's not possible to get unbiased content on the internet. Everything exists with an agenda behind it, for the sole reason that hosting anything is going to constantly cost money.

This wasn't a huge deal when individuals were paying to host and share content to a small audience, it was a small amount of money and you could see their motives clearly (a forum for a hobby, a passion project, an online store, etc...).

Social media is different because it presents itself as a public forum where anything can be shared and hosted (for free) to as many people as you want. But they're still footing a very large bill and the wide net of content makes their motives completely opaque. Nobody cares that much about the headaches of maintaining a free and open public forum, and any profit motive is just another way to sell manipulation.

But that's not profitable.

rational discourse is one of the valuable options possible.

Yeah, can't say that I've seen a lot of that on social media.

You don't need social media to do rational discourse, anyway. All you need is two-way communication, a problem that the Internet solved long before any Facebooks or Twitters popped up. You can have rational discourse on IRC, an email list, or even through instant messaging.

throwing away the whole internet because Xitter sucks is throwing away the baby with the bathwater.

I know you're being hyperbolic here, but unfortunately there are a lot of people now who really do see social media as "the whole Internet". And they have thrown a lot away as a result.