This is a simple question with a simple answer.
Life has no necessary meaning at all, for those who reject Jesus Christ's offer of resurrected life eternal in Heaven.
It is the outcome of resurrected life eternal that gives meaning to this temporary and entropic mortal life. Without this outcome, mortal life lacks the context which gives it meaning.
To reject Jesus Christ's offer is in the power of each and every person. Everybody chooses whether of not to be resurrected.
But if a person chooses Not to be resurrected, one inevitable consequence is that his mortal life on earth will be meaningless.
This is because mortal life is designed as a necessary phase en route to resurrection. One cannot have resurrection without going-through the phase of mortal life.
And each individual person has an unique experience of mortal life - some die almost immediately and are not even born, others survive to become babies, others to various stages of childhood... and some live for many decades. Plus, of course, each person has an unique mind and body, an unique family (or other) circumstance, an unique social experience - and makes his own choices which affect all of these...
What any specific person's mortal life means; depends on that person's nature which he brings from pre-mortal spirit existence. These range very widely from those who are born greatly good or with great abilities; to the vast majority who are born with strong tendencies to choose evil, without much (or any) apparent capacity for love, and with all kinds of deficits, pathologies and disadvantages - presumably some are innate to that person, some are intended by God.
What we make of life, whether we fulfil our primary destiny; is up to each individual. But we can be confident that God will (sooner or later, somehow or another) provide the necessary situation, present each with the vital choice that he needs to make.
In sum: when a person who has rejected Jesus's offer of resurrection to life eternal in Heaven then complains that his life is meaningless and has no purpose; he is correct.
His life is indeed meaningless and has no purpose.
But that has been his own choice.
