"Context dependent" here means a different thing than it means in English, where the pronunciation of letters depends on the word they're in, without any hard rule. To the point of being pronounced in different ways even in homonyms: e.g. "tear" noun and "tear" verb.
The fact that there are a few rules on how to pronounce combinations of letters (and even a few exceptions here and there) has nothing to do with the total mess that is English.
Would it be sane to have a special letter to distinguish the "p" in "park" from the "p" in "spark"? In some languages, it's important, but these two sounds can be represented by the same letter in others because they don't "compete" for the same contexts.
Or how about G? It makes one sound before I or E, another before A, O, UE, or UI, and yet another before UA.
Lots of folks think their language is simpler, but it's only because they can follow the rules so well they don't need to actually know them.