> Why does this tool in the language need to exist? The answer cannot be because Kanji make things easier to read, else you wouldn't need tools to help you read Kanji
This just isn't true. Even most native JP speakers agree that kanji are oppressively hard to learn and remember, so if it were feasible to get by with kana alone, then at least some native speakers would do it in some contexts. But outside of language learning it's virtually never done, and there's a reason for that.
Also, I think you're overlooking that Chinese and Korean have a lot more vowels/tones to work with than Japanese. There are a lot of Chinese-derived compound words that are homophones in Japanese but not elsewhere.
"Science" and "chemistry" are homophones in Japanese: We have special disambiguation reading for "chemistry", bake gaku, used only when misunderstanding is suspected.
There are numerous other examples. Those are all unnatural sounding, mostly industry/field specific, and not replacing the main homophone readings.
This just isn't true. Even most native JP speakers agree that kanji are oppressively hard to learn and remember, so if it were feasible to get by with kana alone, then at least some native speakers would do it in some contexts. But outside of language learning it's virtually never done, and there's a reason for that.
Also, I think you're overlooking that Chinese and Korean have a lot more vowels/tones to work with than Japanese. There are a lot of Chinese-derived compound words that are homophones in Japanese but not elsewhere.