I don't agree that there's only a single prescribed method that everyone should attempt to emulate. This method was incisive and memorable. It drove the point home very effectively. She brought real world examples instead of just hypothetical fears. Her sarcastic delivery implied that the council's position was gleefully evil and comfortable with authoritarian abuses, which should give them pause and make them consider at least how they're being perceived, much less what their actual motivations are. And she offered real world consequences by mentioning their reelection. Greta can do it her way. This woman should continue being herself.

Greta Thunberg demonstrated what a young female orator stating the obvious can achieve.

She achieved some virtue signaling responses that didn't actually improve the issue from the side that was already pro and being called a sock puppet from the side that was con.

What Greta has achieved in modern times with her actions, not with speeches, is way more powerful.

In my experience, this kind is speech is very effective for people who already agree with you in principle, but aren’t mad/motivated enough to take action on the issue. I agree is probably not the most effective at changing minds, but as a kind of rallying call it works.

You must be old. This is how the younger generation communicates.