Okay, if not trusting the Chinese numbers to be exact, we can't be sure they are. But the numbers for Wuhan, unless fictitious and hundreds of people dying aren't being counted, show the reduced incident rate over time.
And this stands to reason. Infection can't pass to new bodies if there's no contact. People flying into the country with the disease will spread it meaning yes, there could be more cases across China. However, if those infected are isolated, it will die out.
The numbers are all correct, but just measuring different things. eg.
"If one assumes that the number of asymptomatic or minimally symptomatic cases is several times as high as the number of reported cases, the case fatality rate may be considerably less than 1%," Fauci and colleagues write."
That's absolutely true, likely less than 1% of people with a SARS-CoV-2 infection in China in that period was dying. If you look at it that way, it's no biggie. But then when you look at the other numbers, 15% of people developing complications that need treatment, and the finite capacity for hospitals to treat people, you see that if too many people get sick too quickly, they won't get the necessary treatment and there will be more fatalities.
I'll run you the stats from the UK again, assuming you trust those numbers.
It's presently 273 confirmed cases. Yesterday it was 244. Two days ago, 209. 164 before that. That's an average growth of about 20%, although one could be more optimistic and call it 12-13% ballpark figures. There have been three deaths, so 1%, and that's not counting the hundreds of unreported infections. That doesn't sound so bad. At 12% growth, that 273 cases will become 2633 cases by the end of the month and 400 people needing hospital treatment. The following month, if the growth isn't curbed, that'll be up to 80,000 with 11,000 people needing medical care - the hospitals won't be able to cope, not just with the Covid19 treatments but also other usual medical concerns. There won't be enough treatment possibilities to save those at risk, increasing the mortality rate. By the end of May,
350,000 people will have needed medical treatment (from 2.25 million infected). And to finish off, by June, everyone will have had the infection, and those 10 million who developed complications will be largely starved of medical treatment. Those aren't just the elderly (a cold argument could be made to let them die off and reduce the economic burden of unproductive members) but also younger people with other conditions such as kids battling with cancer with a good prognosis of recovery but who'll succumb to the added stress of a Covid19 infection.
That's why measures are being considered to slow the spread. In and of itself, Covid isn't a killer-doom disease. It won't knock out entire civilisations and break our food supplies or anything. However, if left to progress unchecked, it will eventually affect many thousands, if not millions, of people who will die without medical treatment and who can't get medical treatment because there are too many people needing it all at once. By taking the disease seriously and limiting it's spread, it's mortality rate can be kept more at the 1% than the 5+% it could be. By comparisons with other diseases, some spread faster but don't have as high mortality, so it doesn't matter so much if they spread, while others kill far more people but don't spread so quickly or widely. Covid19 sits in a middle-ground making it very dangerous*.
* Depending on your definition. For some, 'dangerous' means to them and their family, and if young and healthy, they may consider the threat overblown and not be in favour of measures that impact their QOL for the health and welfare of people they have nothing to do with and don't care about.
Edit: As a personal perspective, I've never taken notice of any of the previous 'OMG we're all gonna die' diseases. Swine Flu, SARS, flesh eating bugs, etc., headlining newspapers were just scare-mongering. Coronavirus is the first I've taken seriously having looked at the numbers myself. At first I didn't think was a huge concern when you think 90% aren't going to be that bothered by it, but when you follow the data to the logical conclusions, and think about all the people you know with medical conditions or elderly relatives and the like, you realise there's a very real potential here for very real suffering and a huge scale. Not just the illness, but the fallout as well. Poor people deprived of medical treatment might end up turning on rich folk paying for private health care, for example. Not to mention moronisms - two youths in the UK beat up some Chinese saying they didn't want Coronavirus in this country.