IMO the term is so diluted as to be meaningless.

Burnout isn't a mid-life crisis.

Changing your career doesn't necessarily mean you're having a mid-life crisis.

Changing your personal circumstances doesn't necessarily imply a midlife crisis.

Every definition I know of includes a sense of existential angst, a feeling of regret, of lost potential, of questioning identity, of a fear of mortality.

But simply realizing you're unhappy in your life or circumstances and want to change them isn't itself indicative of a mid-life crisis by any meaningful definition I'm aware of.