Control of information fails, not because the organisation controlling gets worse at it, but because it gets better at it.
This may sound counterintuitive, but it's not.
The issue is that organisations that can control information want that power for a reason. That reason is always the same: it's economic. Even in the west, where control is much less pervasive. They want it, frankly, so they can steal from "the people" without them noticing.
Currently China is lying about economic things. And people don't care. The government says things are going well, and it appears things are going well. Until that changes there won't be large scale changes. But there's kinks: How many people got fired in the massive mine cuts last year (everything growing at 7% per year, then "boom!", massive protests followed by executions in a dozen cities. Protests that were big enough that suppression didn't work. Everybody knew someone who was aware of the protests). How badly the metals industry is doing. And the macro Chinese economy. How many loans, and where. People are currently largely trusting the official stats despite them being somewhat obviously falsified. There's a few high profile somewhat-loony exceptions (e.g. Kyle Bass). This can't end well ...
And once it hasn't ended well, needless to say, people notice once the cheese is actually gone. No amount of information control is going to change that. That's when information control fails. That's when people start trusting the word of a drunk sailor more than the official newspaper. That's when every organisation that matters switches to it's own internal information gathering.
That will happen. It's a matter of time. There's lots of variables in it, but how good the CCP is at controlling information is not actually one of the variables.