The only time I've ever used a canned response is when I'm out of office:
I'll be out of the office returning xyz. Please contact xyz in the interim. Thanks.
Until that point, my email responses differ no matter how many times I've tried to establish a template. I've sought to keep emails to three sentences, to write them in succinct bullets points, to use colors like red and yellow to stress importance.
No email response is ever really the same since the context, and the receiver is almost always different. That goes for one-word responses as well. That still takes time.
There's no such thing as a canned response, and there shouldn't be. Unless of course, you call me and get my automated voice mail. But who leaves a message for anyone these days?