They're not perfect, but over the last 30 years they lifted half a billion out of poverty and didn't wage war all over the world.
Not everything needs to be wrapped in our style of propaganda, sometimes it can be wrapped in other brands instead.
By contrast, the Great Leap Forward alone killed 16 million, and that's at the lower end of estimates. The population of China at the end of this was ~665 million, meaning they killed 2.7% of their population just in the Great Leap Forward.
So even with the numbers most favorable to China and least favorable to Taiwan, Taiwan comes out ahead by an order of magnitude.
Why is that? How come some things are marketed extensively to the American public but others are never mentioned?
(Also, if the goal is to criticize maoist China, I'd go with the cultural revolution instead of the great leap forward)
There are two reasons why they aren't mentioned as much as Mao's atrocities. One is that those countries are our allies, and as a result we are more willing to overlook their faults. And I don't think that's necessarily right, but it's part of human nature to overlook the faults and flaws of friends and allies. But the second reason is that, even ignoring those effects, Mao killed far more of his citizens (and far more per capita), making it a much more interesting and disturbing event in history. The atrocities of Taiwan and South Korea come across as "run of the mill authoritarian leaders violently cracking down on dissent" while the atrocities of Mao's China are on a whole different level.
FWIW, as far as dictators and genociders go I think Pol Pot gets the least attention relative to the scale of his atrocities since he wiped out 25% of the population, and in extremely brutal and arbitrary ways.
Like you said, it's all about which side people are on. And I agree on pol pot. The only self-genocide I'm aware of in the record.