Some words can be changed, such as those cited, but a huge change can never occur because of regional differences in pronunciation especially involving vowel sounds in many words, e.g., ice, check, cash.
Bingo. The main difficulty in adopting a universal pronuciation-based spelling system is that there is no universal pronuciation.
Also, as another noted, the spellings of our words often reveal their lineages and allow literate people to figure out what unfamiliar words mean, or see the connection between them.
SD