There are lots of people in the world who are impossible to satisfy, who blame all failure on everyone but themselves. They have complaints about everything, justified or otherwise.
By bringing these things up, a person who does not otherwise know you has two possibilities:
- The company you worked for really was that bad. This claim cannot be verified in a meaningful way.
- The candidate you're interviewing is one of these dreaded negative nancies who will disrupt your workplace as they proceed to complain about everything and redirect their own problems upon other people.
Since there is no way to tell which is true, and I have no incentive to trust you, and every disincentive to bring in someone like that into my office, I will not hire you.
Direct, concrete criticism is fine. "We used the waterfall model and I don't believe it works" - but do not come off as bitter, because that's exactly what the Negative Nancy typically sounds like.
If the company was badly organised, behind the times and resistant to change, I don't think there's anything much wrong with saying it. IMHO.