I very much doubt it's an authoritarian nightmare (that would be North Korea or China back in the days of Mao).

China does however have a system of "social points", so people are well aware that if they don't do and say the right things, it might negativelly impact their lives (you don't set up such a system for anything other than push people to behave in certain ways).

Further, only an idiot would deny that during about 3 decades (though that was mainly over about a decade ago) China has pulled up from poverty more people than the rest of the World combined, by a huge margin, even while in the West social mobility went into reverse and inequality started growing (especially after 2008).

Equally only an idiot would deny that in a single party system being openly critical of the Party is likely to have negatives consequences for that person and even the mere concern that it might happen will make people just say nothing, just in case. (I mean, shit, people will naturally just do this at work in supposedly free countries with work-at-will legislation were they can just be fired for no reason, so it takes quite a lot of naivety to think people will not "keep their mouths shut, just in case" when it's actual authorities with no independent oversight over them keeping a keen eye on a persons sayings and doings, as they have the power to fuck your life up far more than merelly firing you).

Finally, it takes are a very (very, VERY) special kind of idiot to think that there are only two ways to govern a country and if you're critical of one of them, then you must be a brainwashed tribalist supporting the "other" one. There is no bigger kind of political moron because the very mental architecture the use to judge things hyper-simplistic and ultra reductive.

If people's life was amazing, the authorities there wouldn't need a Great Firewal of China, a social points system or a giant civil society surveillance system, just like in the supposedly free West you see the increase in civil society surveillance and the Propaganda machine (around here using immigrants and even people with non-normative sexuality as scapegoats) going into overdrive, all coinciding (by "an amazing coincidence") with the time when quality of life stopped improving and started going down and the first generation in a century who is expected the have a worse life than their parents started coming of age.

(Against, this kind of shit should be familiar to Spaniards, at least those who were adults during the days of Franco, because very similar tools were used).

Those kind of mechanisms aren't deployed against a people which supports by 90%+ the current government, and they're generic rather than a China-only thing and some are just as much used in supposed Democracies as in Autocracies - similar techniques, just with different excuses justifying their use.

Whilst the country is not an absolute dictatorship, Chinese "we love the Party" data is highly poluted by a "it's best not to say certain things, just in case" concern, information control and internal Propaganda in a similar way to, say, the public opinion in Hungary is shaped by that regime's control of the Press and a certain insecurity so if you work for the State over there you won't be critical of Orban and his party because that's just not good for your career (and a similar thing happens in, for example, Turkey) so their data on it is going to be highly poluted (unsurprisingly, if you personally know people form those countries, its the more well informed people who think worse of the government, hence typically even with all the information control and even iron first, they have worst polling in the larger cities)

What shocks me is that somebody supposedly from a country which had a dictatorship until 75 can't recognize certain kinds of mechanisms which I'm pretty sure their parents or grandparents are familiar with and their impact.

That doesn't mean that most people in China aren't content, what it does mean is that poll data showing a 90%+ stated approval of the government must be taken with a large pinch of salt.