I utterly dis-agree with the notion that "this is a good and valid thing to say." And, I would specifically point out the following sentence from your OP:
"The reason I want to leave too is because I have seen too many cases the bosses cannot drive the company very well and how they deal with the clients and past employees."
So, the reason why you want to leave is "somebody else's fault." Uh huh. Just how many "clients" or "past employees" have you dealt with, and just how many cases is "too many?" If you said any such thing to me at an interview, I assure you that the interview would be finished. I would be polite to you, of course, for a few more minutes ...
(Yes, I have sat on "that side" of "that desk" many, many times. I now have over 35 years' experience in IT.)
Maybe the manager is a screwball. Plenty of managers out there manage "a revolving door" of people who quickly move-on to better opportunities. But, what people do not do, is: "quit."
Say nothing negative about your present employment situation. If you find it disagreeable, and want to quit because it is disagreeable, then any interviewer would realize that you're likely to find their job "disagreeable," too. (So to speak, "every job sucks...") The only reason why you want to move from one job to another is because you see it as "a move up" for you. A better opportunity. A better chance to use your exquisite skills and experience.
You must also be careful to present the impression that "when the going gets tough, I will not 'get going.'" And, you must sincerely mean it.
The reason I want to leave too is because I have seen too many cases the bosses cannot drive the company very well and how they deal with the clients and past employees.... So ...you just gave us the reason you want to leave, which is very different from "because everyone else is leaving".