Pretending this conflict could easily be solved over a specific line isn't reasonable, especially when the other side can go back in time and find an equally valid reasoning... But.... Only one side has regretted they should have accepted the 1947 Partition plan.

And before then, it was the British mandate and ottoman control.

https://www.reuters.com/article/us-palestinians-israel-abbas/abbas-faults-arab-refusal-of-1947-u-n-palestine-plan-idUSTRE79R64320111028