It's not just kanji, it's also the entire vocabulary being used.Kanji use has been reduced in modern times. Many Japanese today can’t understand WW2 era letters because Kanji was a lot more commonly used even 70 years ago.
For example, contrast a line taken from the Japanese declaration of war against United States and British Empire: "朕茲ニ米國及英國ニ對シテ戰ヲ宣ス", with its translation in modern Japanese
This is because formal writing of that era was evolved from sōrōbun (候文, the original pseudo-Chinese, if you will), which looks like something like this: "新年之御慶目出度申納候" (Well, not exactly. What is printed out as computer-readable text is a lot more normalized than what was actually written out with a brush pen), which in turn was ultimately evolved from Classical Chinese.
To bring it back to pseudo-Chinese, since it's an Internet meme, there really isn't a canonical form. Its resemblence to Chinese is dependent on the writer's familiarity with Chinese and its vocabulary. Sometimes there is actual unadulterated colloquial modern Chinese embedded in it (thanks, momio and Azur Lane). Can't post any example though, because that will get me turbo-banned from this forum
Make no mistake, this does not mean that modern Japanese people can understand modern Chinese or vice versa with just some simple modification. The languages have drifted too much for that. Hell, it doesn't even mean that modern Japanese people can understand Classical Chinese without some serious annotations and explainations... then again, the same thing could be said of modern Chinese people as well.