The verse is almost administrative. Abram leaves Haran at seventy-five. Lot goes with him. The Targum in (Genesis 12:4) does not embroider — and that restraint is the whole lesson.
Targum Pseudo-Jonathan reports the number plainly: Abram was the son of seventy and five years at his going forth from Haran. Seventy-five. The patriarchs of the Hebrew Bible grow old in reverse. Noah begins his ark at six hundred. Abram begins his covenant at seventy-five. Moses receives his call at eighty (Exodus 7:7). The founding gesture of Jewish history is not a young man's gesture.
The Targumist, by refusing to expand, lets the number speak. Age is not a disqualifier in this tradition; it is often a credential. A man with seventy-five years of disappointment behind him, seventy-five years of watching his father not finish the journey, has enough history in him to hear the call without flinching. A younger man might have been too certain to be useful.
And notice what follows. Lot goes with him. The Targum preserves this detail without comment, but it matters. The call said separate from thy kindred, and yet a kinsman follows. Abram's obedience is not perfect. He leaves father and land but not nephew. Every beginning is a little compromised at the edges. The Holy One accepts the journey anyway.
Seventy-five is not too late. It is, sometimes, exactly on time.