I can read only a limited number of kanji (or rather, words written with kanji), but even that makes reading much easier. Books for small children are written in Hiragana, with spaces, and in theory that should be as easy to read as English.. after all, it's easy to learn Hiragana, anyone can do that in a short time, and with practice you can learn to read it fast. But it's still tricky to read all-Hiragana sentences, even with spaces. Not sure I can explain why, more than the usual (and true) argument about the particularly large number of homonyms in Japanese. It's more than that. It's just much faster and easier to read 私 than わたし
It's interesting to consider that Japanese's relatively low number of discrete phonemes might result in a relatively high number of homophones, but if a preponderance of homophones is the problem, wouldn't listening to spoken Japanese be just as hard as reading hiragana?
On the contrary, listening to Japanese feels easier than listening to a lot of other languages, even for speech which you don't actually understand. The sounds are simple, there are a lot of vowel sounds. Straight forward vowels, not diphthongs, and in that respect it's a lot like listening to (slow) Italian.
There are a few run-on consonants in speech, but not many. Of course one runs into homophones in speech too, but there you also sometimes (but not always) have pitch to help you (persimmon and oyster are both written かき(kaki) in Hiragana, but the pitch is different, same for chopsticks/bridge), and there's context - if you understand enough of the language.
As an example, my wife owns a Japanese CD which includes a couple of songs originally from my own country, but translated to Japanese. Listening to that is very easy, I hear every word.. it's much much harder to actually get the words if I listen to the original in my own language! And these are simple songs.
EditAdd: What I said above is correct in the sense that it's easy to listen to Japanese, as in actually hearing the words, but yes there are homophones which sometimes make me, a low-intermediate speaker, not understand what I hear. I hear "another" similar-sounding word, unless there's pitch to clearly identify it, and then what I hear doesn't make sense unless it's a recording and I can re-listen.
