This is simply not true and believing it is so is madness:
Dennis Blasko, author of The Chinese Army Today, observes that the CCP's ground forces, like the navy, are not yet ready for the ultimate fight. For invasion to be a realistic option, China would have to have far more helicopters, paratroopers, special operators, amphibious mechanized divisions, and marines. Moreover, the PLA would need to build a solid non-commissioned officer corps and provide better training to unit leaders up and down the entire chain of command.
I guess the PLA didn't conquer the island of Hainan in the civil war. I guess the Germans didn't conquer Norway and Crete in World War II and that Japan didn't conquer the Philippines in World War II.
I guess there were no American amphibious operations in Europe during World War II because there were no Marines deployed in Europe for that mission (and certainly no helicopters!).
Indeed, I have to assume there were no amphibious landings in history prior to the introduction of helicopters, paratroopers, and mechanized divisions--the possession of which is an absolute requirement, I'm to believe.
I must assume that three Chinese airborne divisions in an airborne corps isn't enough to invade.
China can invade Taiwan--going right for Taipei--if they are willing to endure the casualties required to do it. In 2004, apparently 21,000 dead was too much to pay.
And what happens if "only" capturing the biggest core interest of China isn't the objective of the invasion? What if the Chinese people become so upset at faltering economic growth that rallying the country around the Chinese Communist Party against a foreign enemy to maintain its monopoly of power is the objective? What level of casualties would be acceptable to China's rulers in that case?
Would even losing such a war be an acceptable price to pay if the CCP retains their monopoly of power?
Saying that China can't mount an invasion that would look like one of our World War II amphibious invasions isn't the same thing as saying China can't invade Taiwan. The Chinese marine corps is a red herring when it comes to Taiwan.
And given that even America lacks the amphibious lift to conduct a large-scale invasion these days, I guess nobody can invade anybody? Is that the argument?
China sure acts like it wants to invade Taiwan if necessary. And the little grey men are already destabilizing Taiwan, it seems:
Wang Ting-yu, chairman of the defence committee in Taiwan's parliament, said Chinese spies were masquerading as academics or business people.
He claimed Beijing was trying to sow chaos within Taiwanese society.
China considers the self-ruling island territory that must be reunited with the mainland - by force if necessary.
Taiwan needs to arm up and train like their life depends on it; and we need to be ready to intervene before China is ashore in force on Taiwan and rattling nuclear sabres to keep America and Japan from intervening to halt and throw back the invaders.
China doesn't need to complete their conquest of Taiwan the way Russia conquered all of Crimea in one nearly bloodless operation; China just needs to successfully grab part of Taiwan prior to a ceasefire to advance their territorial claims the way Russia has just part of the Donbas in eastern Ukraine.
UPDATE: The Chinese are committed to winning that ultimate fight:
"Separatist Taiwan independence forces and their activities are the greatest threat to peace and stability in the Taiwan Strait," Chinese Defence Ministry spokesman Wu Qian said at a monthly press briefing, according to Reuters. "It is futile to 'use weapons to refuse unification,' and is doomed to have no way out."
Note too the Chinese logic. When the Chinese storm ashore, the threat to peace and stability comes from Taiwanese resistance and not the Chinese invasion.