It's going to be a change of life style for Messi & his family if they move to SPL. Life's different for him in Inter Miami because his kids & wife moved there. He doesn't want to move them to a new country but Al Ahli's offering a mega contract so it won't be easy to say no.
For someone like Messi who has achieved everything he needs, Saudi offer might be outrageous but if he doesn't want the contract then he would neglect the offer, sometimes players value family over contracts as long it's not adjustable to be convenient he won't accept the offer from Saudi. Messi may not consider the move to Saudi for personal reasons, he might consider continuing his football carrier in US.