That's a cool text. It feels like the language switches to old dialect. It reads and probably sounds a lot more like old german or dutch.
Old and Middle English were like that too, but then the Great Vowel Shift happened and now English still mostly retains the Middle English spelling with apparently random pronounciation rules.
Nobody devises a non-phonetic alphabet, when English adopted the Latin alphabet it was mostly phonetical. The issue is that the written language always moves slower than the spoken one, because written language lasts for longer.
A is /ei/ and lots of other sounds.
E is /i/, sometimes it's an open e, ..
I is /ai/, sometimes not, ...
O is always a diphthong, plain /o/ does not exist anymore
U is /a/, /ju/, ??
Y is there for the show, often it's used for /j/
English like German has lots and lots of vowels, while Latin and Italian have like, 7? The letters were supposed to have only one sound at most, but history clearly shows us that it's easier to reuse or adapt an existing letter than invent a new one (look at [ng] for instance, or [th] which became used mostly because nobody had types to print thorn and eth).