As I see every day in students' papers, computers can't read minds. They can't distinguish between it's and its , roll and role , principle and principal , breeches and breaches , deference and difference , or for that matter, identify as wrong any word that incorrectly appears as another word. But there's room for improvement. Remaining ones, as well as homonyms, could be dealt with by an advanced spell check that queried all genuinely ambiguous cases. Of course, language is never static.
Usage constantly struggles with rules and frequently wins.
The spell checker may well be creating a new usage. It will be interesting to see which gives in first-the software writers or the English language. Another problem is that computers do not correct handwriting. Here ingenuity fails me. Maybe it would be simpler just to learn how to spell.