Would you buy a pair of speakers by just looking at the measured freq. response?

Maybe add a little. I’ve come to learn that certain reviewers like a ragged response in the tweeter. I do not. Mind you, I did not first look at the response and hten decide what to like, I really disliked two speakers I had listened to in person for having a treble response I found unlistenable, then I read the reviews with measurements and went AHA!!

That ragged, up and down response between 3 to 10khz really bugged me, but the (very important and famous) reviewers praised both these makers for the same reasons, calling one a poor man’s version of the other. Ugh.

Also, a speaker like modern Dali, many models have stepped up mid-tweeter response. I can hear it and you can see it in the plots.  BTW, this design has it's uses I just am not looking for that.

So, while I would never buy based on measurements I’d probably avoid a few based on them.

No.

Off-axis response, impulse response, dynamic range, distortion, all matter. 

I also have to say that, by the same token, I wouldn't buy a subwoofer and configure it based on published specs either.  The speaker in the room is a very different beast than the speaker in the lab.