By your logic, we should turn the US back over to Indian tribes.
Which Indians among the many, with multitudinous languages among them? Which non-nomadic state? Or do you imagine there they all were one, and or all lived peacefully with each other, and all remained in one area?
And who did they displace, if any? Should it be given back to Asians or whoever came here first from Africa?
Of course, genetics themselves do not define a nation. As for Israel, if any of the organized Canaanite tribes that the Hebrew nation defeated (but did not totally exterminate) come back and want to reclaim their land then they can fight for it. Or the past conquerors of the land.
Islam is what basically makes the Palestinians (which they did not call themselves) one people, but that false religion certainly \came after the Hebrews, while they never established a state in the land of Israel.