Stifling censorship has enforced a silence over those who try to keep alive the memory of the protests and massacre, and has scrubbed the internet in China of virtually any references to the upheavals. The country has become increasingly authoritarian under Xi Jinping, the leader of the ruling Communist Party, whose administration has rounded up rights lawyers, labor activists, students and Muslim ethnic minorities.

“I’ve felt increasingly isolated,” Mr. Zhou said in an interview in Beijing ahead of the 30th anniversary of the Tiananmen crackdown. “Not many people care about June 4; young people don’t even know about it.” He was speaking in a cafe in north Beijing where other customers, eyes often fixed on their phones, seemed a world away from the talk of demonstrations and bloodshed.

Mr. Zhou’s daily reality is a stark reminder of how successfully China’s ruling Communist Party has married economic growth with authoritarian rule over the past three decades, resoundingly rejecting calls for greater political freedom.

But even more unexpected to Mr. Zhou were the troubles in Western countries that he admired as models of liberal democracy. The political divisions under President Trump and Britain’s Brexit shambles showed that even mature democracies could fall prey to dangerous populism and demagogy, Mr. Zhou said.