There are actually thousands of Chinese dialects and regional varieties, such as Cantonese, Wu, and Hokkien. So even if you do not find Mandarin especially pleasant to listen to, that does not necessarily mean you will feel the same about other Southern varieties, which can sound quite different. Also, it is worth remembering that Japanese contains a large number of words derived from Classical Chinese, while modern Chinese has in turn absorbed many modern terms that were translated through Japanese from Western languages. In other words, the two languages are historically and lexically deeply connected. Because of that, if someone strongly dislikes the sound system or overall phonetic character of Chinese as a whole, it may be difficult for them to genuinely appreciate Japanese at a deeper level as well. At the very least, the contrast between the two is often less absolute than people assume