> Isn't that an accurate definition of what "loser" generally means?

"Loser" is a catch-all taunt that bypasses empathy. But certainly they might be 'in a losing situation', which is an important distinction.

> Except for the "disabilities" part, which is problematic to classify

Disability in this context is something intrinsic to the person (e.g., physically, mentally) that makes the employment process substantially difficult to engage with.

In addition to disability, difficulty can also arise do to any prejudice that might be levelled against them (e.g., ageism, sexism, junior vs senior, skin color, language skills, country of origin), as well as visa consideration, financial situation, etc. There's so many things that affect the risk calculus of changing jobs.