See: Manna by Marshall Brain. In his Australia project they simply install a centrally controlled "cutoff switch" - when people are out of line their conscious brain gets switched over to a virtual reality where they can live out their fantasies while their bodies report to detention until their brain decides it wants to join "the real world" again.

people do not know how to act properly

They do, in communities where rules exist and are enforced. Anonymity may lead some people to feel more emboldened to act out, but when handled properly I believe the vast majority of them will just settle down and either learn how to participate in good faith or find somewhere else to be. The bad behavior patterns we see in some places are, in my opinion, the result of insufficient social norms and enforcement thereof. This is also a situation capitalists will foster, because it drives engagement and inflates content.

Unless we can force people to act with civility - which implies people being fairly conscious of the consequences of their words and actions

So you already understand that this is a problem that only exists in places where bad actors are given license to continue acting out.

Where’s the structural societal incentive to “do so much good”, and why would we need it?

That's a great question. There are some college courses that can help you answer that. The short answer is "because in terms of the flourishing of an entire species, cooperation trumps competition, but it's a recent evolution and doesn't come naturally to everyone". If we are to flourish and advance instead of strangling ourselves in the crib, we need to stop tolerating the kinds of selfish behaviors that prove detrimental to every society that permits them.

That may be true, but TV also brought me Star Trek TNG, Captain Planet, Sesame Street, Mr. Rogers, and many others that instilled values in me that are core to who I am today. Let's not let perfection be the enemy of progress, and keep working to put our tools to better use.