It is true that your word-processor's spellchecker does not and cannot improve your English as you'll never learn if you don't make and not humiliated by your mistakes.
But at the same time new technology gives courage to write. Ordinary people would have terrified if they were stuck with an old typewriter.
What technology did remarkably well was to empower people and encourage them to focus on the content and expression by relieving them from checking ruthless grammar and spelling errors (not completely but nearly). And I think this is a good thing. Technology democratised writing.