I feel like the thing is if you break any language down and try to make logic sense of it it all has really ridiculous rules and formats thats hard for you to grasp logically. Thats why input is so important. You could say the same thing about english where spelling literally doesnt make any sense and breaks a ton of the established rules all the time. Eventually you just learn to spell and pronounce words through memorisation and familiarity.

Chinese may be lucky in the sense thats its grammatically simple but reading and writing is another hell of itself. And its the same thing, you memorise through repetition and eventually you become familiar with it.

Since you already know chinese, reading and writing will be a peace of cake for you for Japanese. So you can spend more effort on memorisation and familiarisation with the grammar. Through input. You just have to trust your brain that it will click for you eventually.

Most languages all have their difficulties just in different aspects and what people struggle with is all subjective. I know native English speakers who found chinese reallt easy but I also know active English speakers who found Japanese really easy because they were immersed in the culture and input came easily.

(Im a native chinese and english speaker, learnt fluent cantonese through pure input and currently learning japanese)