Is it a bad thing if a job applicant's CV has several short-lived jobs? If yes, should it be seen as a bad thing?

I've seen several people afraid to quit early in jobs they're miserable in because they're afraid how it would look in their CV, and also some elder generation telling people that same thing.

Is it really a bad thing if a job applicant changed jobs a lot?

What's the cutoff point for "a lot"?

Should it be seen as a bad thing in the first place?