Yes, it is definitely other people, even before I saw your response. Imagine you are literally the only person left, what would be the point of anything.
To contribute to a future where we can understand the nature of reality and discover answers to important questions. Most other goals are artifacts of evolutionary pressures or become counterproductive in a world of abundance (i.e can be reward hacked).
Not being worth something (money). Being worth something to someone (relationships).
You can kind of get the "being worth something to someone" by achievements, but they have to be achievements that other people care about - that move them, or matter to them in some way.