It was failed because it didn't fix grammar. It functioned more like a spell checker, replacing things like "itd" with "it'd".
It couldn't detect context, or repair sentence structure. It couldn't understand the tense of sentences, it couldn't correct basic errors like than and then.
Rather than fix sentences, it had just as much change of breaking them. If you type "What is your Blockland ID" it'd turn it into "What is your Blockland i'd" because it didn't understand word usage.
It was just a stupid toy. A string replacer.