Chinese here. hmm, last year when tianwen-1 was launched they said they will land sometime in the first quarter of 2021. They didn't announce a specific date because this is the first time we sent a probe to mars and they need to gather detailed data of mars to ensure a good landing. For example, high definition scan of the landing area and weather patterns. There are many systems in production use for the first time. For example, deep space communication (we never sent a probe this far). Or mars geo-positioning system (How does the probe know where its located in space with relation to mar's surface, how does it know when and where to release the lander to ensure it lands on the target). I am sure they need to gather data and validate these systems. This usually is a full mission itself. So I don't think its surprising that once all the research and validation is done can they announce a date for landing.
As for secrecy. I believe it comes mostly from CNSA's lack of confidence. This is the first time they ever sent something this far and they are attempt to land all in one go. Its daunting to think all the systems that have to work right on the first try. If I were them, I would be unconfident as well. I think they are trying to keep the expectation in check, not wanting to hype the thing. Give them the breathing room if they fail.
Yes, CNSA has strong political pressure to not fail. That's due to: 1) public support for the country continue to spend money on sending fireworks to the sky and 2) public confidence in country's system. But it doesn't mean failures are not tolerated. For example, the long march 5 rocket failed during development, and resulted in 3 year delay in the program and pushed back all the launch missions, like tianwen-1, chang'e5. change5 was supposed to launch in 2018, and it sat in the hanger for 2 years. The chang'e team didn't even know what to work on. But the rocket team got support. Learn from failures, troubleshoot, improve processes. I am sure if tianwen-1 failed, the team will get support. They will learn, and try again. I think the political pressure is not all terrible in healthy dose. It ensures people are working carefully, thinking fully, creating processes and methods, to ensure stuff gets done. Without political pressure, you will see more "corruption" and "bureaucracy".
Also think about what the news will be if china space missions did fail.
tianwen has been in the works for a decade now, they didn't start this recently and time it to ccp's 100th anniversary. The launch in 2020 was because the mars launch window. ccp is saying many years now that they support the space endeavor and what china to progress in science and tech. Support for CNSA only got stronger in recent years.
As for money. Pay is a issue in China for scientists and researchers in general. Especially, in all of the state-owned sectors and public institutions, not just space. Your front line workers will leave when pressure and money are not in balance. Until no one is there working for you. So at some point leaders will realize its not sustainable. And given the political goal of improving science, research and tech in china, pay is going to be a central problem needs to be tackled.
Lastly, I feel like regardless of politics, we should be proud of this moment. 2200 years after 屈原 stared at the stars and wrote the poem 问天，we built a spacecraft landed on another planet, bring Chinese characters to it for the first time in history. 遂古之初，谁传道之？上下未形，何由考之？Does it not have certain romance to it?