It may be "broken" in the sense that it's not accurate to the original language in orthography or pronunciation, but it's great because it's internally consistent for speakers of Japanese. I can look at any foreign word in katakana and instantly know how to pronounce it in a way that is intelligible to other people in the language I'm speaking: Japanese.

Even with the way English does it for other languages that use the same alphabet, while the orthography may be similar, the pronunciation is generally just left to luck and the speaker's/listener's perception of the word's original language.

Fair - English's orthography is definitely worse.