I live with a roommate who is trilingual (Chinese, Japanese, and English) and we talk about this a lot, so I'm not short on knowledge about the Japanese language. I'm aware of the high degree of variability in Kanji use within the Japanese language. However, the fact that Japan and the other East Asian cultures used Chinese characters for a good portion of their history before adopting a more phonetic system would indicate that nothing categorical excludes Chinese from being a universal language. It's the power arrangement of institutions and agents that determine which language system is used internationally, and not inherent properties within the language itself. You may find memorizing Kanji difficult, but a Chinese learner of English will find it difficult to figure out words through a spelling system. It's largely a matter of which one is already embedded in the workings of the world (and thanks to the British, that would be English).
Furthermore, just as Japanese has gone through written simplification, so has both Mainland China and Taiwan. While Taiwan adopted a similar system to katakana in Zhuyin, Mainland China has opted for a romanized system in pinyin, so it's not really a matter of learning to memorize Chinese characters.
Furthermore, just as Japanese has gone through written simplification, so has both Mainland China and Taiwan. While Taiwan adopted a similar system to katakana in Zhuyin, Mainland China has opted for a romanized system in pinyin, so it's not really a matter of learning to memorize Chinese characters.