This is pretty comparable to being asked to be critical of yourself (e.g. "What's your biggest weakness"). Generally speaking this is a bit of a trap and your main goal should be to not take the bait and move on to another topic ASAP. If they really press the issue focus on issues where there's nobody to blame and there's not that much that's going to be held against anybody (e.g. Old Co become very big which was fun but now I'm looking to be part of a smaller team). The key thing is to keep things positive and move on to why you want to work for them instead of why you don't want to work for your old employer.
I don't know about the question being a trap. If you don't try to be too sly about it, you might even turn it into a plus for you. If it were me interviewing, my biggest concern would be that the OP is burned out, and thinks that working at a startup will be nothing but sunshine and lollipops.
Instead try being a bit more concrete: "I didn't like BigCo because of <specific, observable and especially non-judgemental facts go here>. Some people like that, but that's just not what I enjoy. I'm curious to hear if you feel I'll run into the same problem working for you."
If a candidate said that, I'd be more convinced that:
1. The candidate is willing to leave the BigCo world behind.
2. The candidate has realistic expectations of what a startup will be like.
For the record, I think I wrote enough in the original post to show that I'm highly skeptical of startups that claim to have awesome work environments. That said, the community response has definitely been helpful for me to figure out some realistic expectations.
Let me reframe what you just said. Yes, your post does show that. But do you plan on showing that post to any potential employers? It's just as important for you to demonstrate that to potential employers as it was for you to demonstrate it to us. You have to skirt a very fine line between demonstrating that you want to work for them and demonstrating that this want is reasonable and not based in fantasy.
> But do you plan on showing that post to any potential employers?
I probably won't say it in the way I wrote the post, since I think it will be open to misinterpretation that might close some doors unnecessarily. But I will definitely bring up my expectations as a matter of concern.
