You are right to say the problem should not be ignored and reasonable precautions taken by all but I restate that a death rate of 3.4% of those infected (not of the general population) and a reported infected group of less than millions and in specific areas should not be considered more than relatively (note relative numbers) remains miniscule by world historical terms. The great majority of those infected are according to WHO probably uncountable but very significant, and they recover most without even registering it is the virus. You mention the cruise ship: even on a highly infected cruise ship of primarily elderly people many with underlying health issues did not result in the death of hundreds even when quarantine was initially disorganised.
As for the claim that China cannot report the truth and has an economy in ruins, the World Economic Forum states:
"China is the world’s second-largest economy and leading trading nation, so economic fallout from coronavirus also threatens global growth.
Economists polled by Reuters between 7-13 February said they
expected China’s economic growth to slump to 4.5% in the first quarter of 2020, down from 6% in the previous quarter – the slowest pace since the financial crisis. However, the economists were optimistic China’s economy would recover quickly if the virus could be contained."
The WHO and World Bank appear to accept the evidence that China has so far effectively contained the virus even in its epicentre.
The response of sceptics is not immature: there is a downside to over-reaction and extreme anxiety (as in the early days of HIV-AIDS virus) as there is to ignoring real risks. The most severe predictions of infection spread suggest an uncontrolled and uncontained global epidemic could lead to as many as 20% of the workforce off sick for 2-4 weeks but the large majority recovering. That would be very significant but still not catastrophic in world historical terms compared to great plagues of the past and even to post-1918 influenza epidemic.