[RealJames]

I'm scared. ~ 怖い
I'm scary. ~ 怖い
（same, and same with interesting/interested, boring/bored, and other ed/ing adjectives）

I have a dog. ~　犬飼ってる
I have dogs. ~ 犬飼ってる
(same)

いいよ sometimes means, "that's okay" or sometimes "no thanks" and in most situations it's clear but now and then it's confusing even for native speakers.

My friend is so cool, she ... -> in Japanese the she/he is not explicit, so we don't know the gender of the friend, but in English you can explain it passively

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These are some examples off the top of my head where Japanese lacks accuracy and English has it readily available.
I'm sure there are heaps more, perhaps someone better at Japanese could think of more.

I feel that Japanese is somewhat crude and lacks the proper vocabulary to express simple ideas, but like you said, sometimes Japanese can express things much more easily than English, I just feel it's not an even balance...