They don't work this way because it makes shareholder's the most money, not because it is the best experience for the user.
> Advertising plays a very small part in this. Most of what you would call "disinformation" is spread through reposts, which are not affected by advertising.
A completely false ad about a candidate of a different political party is much less likely to be called out or reported because it is only shown to a highly targeted group of people. This lack of accountability creates disinformation. These ads could not be ran as a billboard advertisement or in a non-personalized ad space.
All of the counter arguments always come down to this: Facebook would make less money. And, yes, of course that is going to be the case because if any of these changes would make them more money they would have implemented them themselves. It requires a public corporation to accept that they are making the world a worse place, and to choose to make less money to stop doing that.