It would certainly be great for Madrid if Benzema stays with Madrid this season. But Benzema knows very well, if Madrid gets a suitable replacement for Benzema, then Madrid would throw Benzema away. And so Benzema did not take any risk. He has received good offers from Saudi clubs. This is why he is with the club in Saudi Arabia.
It is difficult to find a suitable replacement for Benzema. Joselu is really talented. There is no doubt about it. Because in the last season he was third in the list of goal scorers of La Liga. He is quite talented. However, he may not be able to contribute to Real Madrid's performance like Benzema. However, if he adapts to the Madrid squad, he can contribute to the stability of Madrid's performance.
Benzema’s form has dropped in recent months because of his age and him being prone to injuries, his move to Saudi was probably the best move for him. Moving on from here is now the next step for Real Madrid as they consider Kylian Mbappe as the preferred replacement but a deal is yet to be agreed on between the two clubs at the moment. Mbappe is also indecisive on where to go, he has mentioned in the past that Real Madrid is his childhood dream club but now it seems that Mbappe is being swayed by the offers from Saudi clubs.