Being prepared for any contingencies is one thing; nobody is denying that the Chinese have been doing that since 1949. Having a plan and timeline to actually going through with a Taiwan campaign is another thing.
We know that the US military have plans for a Canadian campaign, but it doesn't mean that the US is planning to attack Canada by a certain date (although things might seem on the brink these days).
There likely isn't a clear definition of what it means to be "fully prepared" for a Taiwan campaign; these are moving goalposts and there might never be a "perfect" time or condition in which a Taiwan operation would make most sense.
As for public support and its supposed decline (no evidence of this but let's entertain this for argument's sake), their leadership would have to weigh that against the possibility of greater domestic backlash should a Taiwan campaign be unsuccessful or costly. I'm also not convinced that public sentiment is something that the CCP gives too much though about. Suffice it to say, things like public support and the ambiguous measure of isolationist sentiment are trivial compared to the real ramifications and risks of a Taiwan campaign, economic- and political-wise. If the Chinese government has any care about China's society, economic wellbeing, and the living standards of its citizens, it would need to ensure that armed reunification would occur only in the most dire of circumstances (e.g. an imminent and unacceptable threat to China such as the development of WMDs by Taiwan) and when there is near 100% confidence that such an operation would succeed without incurring the risk of economic or military harm.
