> English is not really phonetic anymore, so this approach doesn't quite work well.

I presume you mean it's not particularly 1-to-1 spelling <—> phonetic.

It is highly phonetic, but it does have alternate mappings between individual or adjacent letters and sounds. And silent letters or syllables.

But alternate rules are rarely random. There are usually many words represented by each rule. And those words often have similar overall spellings and phoneme patterns.