Well I would agree it's up to each individual to find their own version of happiness in their personal life, but to think that any job can be made "fun" is silly and only shows that the person saying it has lived a sheltered and privileged life.
Lots of people are in lousy jobs, mainly because of lousy managers. Some people just can't wave a magic wand and put themselves into the job of their dreams. There are other factors at play, some of which are out of their control.
To not hire someone because they were in a bad situation is short-sighted and narrow minded. What is important for hiring managers to consider is, what can the candidate do to solve problems in the job that I'm hiring for? What has gone on at another job in someone's past is irrelevant. As is their past and current salary.
The "no one is ever allowed to say anything negative" nonsense that some recruiters believe in is silly. Some people wouldn't be interviewing for new jobs if something bad hadn't happened at the last one. I guess hiring managers would rather be lied to.
If the person is a good candidate for a job, I'd rather know more about what you're looking for in a job with a potential company and why you weren't satisfied with your previous job, instead of saying everything was all peaches and cream.