But you're right, you need to be careful of implying things you don't want to imply. And if you've worked there for more than a year or so, you have to be prepared for the natural followup question "What changed to make the fit no longer good?"

But the key thing is that you aren't being deceptive, you're just giving the most general answer possible. So the followup question is probably not a stumper.

For instance, when I interviewed where I currently work, I gave this response for why I left my prior job, and got the followup question. My response to that was the honest -- but still vague enough -- answer "the company had been acquired, and I found the new management style difficult to excel in."