What does it mean to "have a life"?

It has a connotation that the person to whom it is addressed is far too interested in someone else's business rather than tending to their own business.

Basically, it reflects disapproval by the person suggesting the need to have a life. Essentially, the person is suggesting the one who lacks a life is not living in a manner the person making the statement feels is prudent.

the idea is to do something useful with the life you have. a life unlived is not a life. You can pass the time of the life, but it is not living.

It means you're still on this side of the grave. All those phrases you listed are just empty words.

"Get a life" is an idiom and catch phrase that has gained international usage. It is intended as a taunt, to indicate that the person being so addressed is devoting an inordinate amount of time to trivial or hopeless matters. The phrase has also appeared as a generally more emphatic variant of the taunt "get a job"[1][page needed] and implies the addressee needs to go out and make their way in the world, without being supported by outside sources such as parents or benefactors. It may also be directed at someone who is perceived as boring or single-minded; suggesting they acquire some other, more practical interests or hobbies and get dates, find a job, or move into their own home.

https://en.wikipedia.org/wiki/Get_a_life_(idiom)

https://www.huffingtonpost.com/dr-cara-barker/life...

If you say that you have a life, you mean that you have interests and activities, particularly outside your work, which make your life enjoyable and worthwhile.

https://www.collinsdictionary.com/dictionary/engli...

https://meyerweb.com/other/humor/life.html

Imho, Jay R identifies the general import or thrust of the "Othering" of "get a life."

It may be helpful to consider that e.g. Husserl and Heidegger might be giving a philosophical equivalent of "get a life" insofar as they comtemplate each other's pov--more evidential is Schopenhauer "vs Hegel," Marx vs most philosophers and philosophizing, Soren Kierkegaard re "churchianity," Aristotle re Platonic "idealism," etc.

In positive-speak, one's "inner child" or "soul" or "memories of kindness, love, truth" (and, for Heidegger, "authenticity" ;-) ---> "life" or even "Life" (as Plotinus, in "One Mind Soul").

Related: "Quarterlife Crisis: The Unique Challenges of Life in Your Twenties;" "The Quarter-Life Breakthrough: Invent Your Own Path, Find Meaningful Work, and Build a Life That Matters;" "Man, Master of His Destiny;" "Understanding Yourself" by Mark Prophet.

how is the world better for you being here that is a life or are you a tree do you make a lot of fruit or money do you flower like a rose then fade or do you do something that will be appreciated for a long time to come and you will be remembered fondly even if you fail there have been many people who were somebody a life

It means having interests, ambitions, friends, a social life, doing a variety of things and making good choices, instead of siting around waiting for someone to tell you what to do and isolating yourself from social contact.

It's meant to suggest that someone has no other interests or awarenesses than in the matter at hand. It's an insult and sharply inappropriate.