You're proposing to make reading just as difficult as understanding every other dialect of spoken English - something even most native speakers have difficulty with.

Your proposal would also eliminate whole-word recognition, which is what makes reading fast. It would slow us all down to the speed of young children just learning to sound out the letters.

Yet people who speak those dialects can write anything down and I'll understand it perfectly with no effort.

You don't understand the value of standardization. It's what makes reading fast and independent of dialect. People who read English don't literally sound out the letters. They recognize the whole word instantly. Sounding out the letters is only a fallback mechanism.

What you're proposing might work for a tiny language with only one main dialect. English is a global language with a huge number of dialects. Major languages like this need standardized writing systems, and to no one's surprise, they all have them.