This article makes no sense; it sounds like leftist propaganda. Advertisers only care about 'brand safety' to the extent that it impacts their ability to sell stuff. So long as users keep using the platform, advertisers will keep coming back - They're not going to vacate the platform and let their competitors get all the eyeballs... If they did, those competitors would gain market share and make incumbents irrelevant…
Advertisers love 4chan type sewers. So do users.
The people who only want to consume government and corporate propaganda will only see content from like-minded people anyway; they will get the safe experience that they want. No problem! Companies can target them and sell them cricket flour, dried maggots, lab-grown meat and COVID booster vaccine number 27... These people won't even realize that the deplorables also use Twitter because they will be in a different filter bubble.