Madrid will remain stable even if Joselu chooses to leave, because as we know, next season they will have two younger strikers, namely Mbappe and Endrick. Joselu will still be remembered as Madrid most successful loan player, that's what many people call him, even though he is a second tier player, we can all see that Joselu played a big role in Madrid's journey to winning the Champions League trophy.
It is reported that Madrid management is still trying to make Joselu status permanent from Espanyol, where Ancelotti also asked him to stay another season, but Fabrizo Romana said that Joselu will move to the Qatar League with Al Gharafa. Joselu understands that competition for playing minutes will be very tight next season, so his decision to leave was the right one. Joselu was very lucky to be able to play for Madrid at the end of his career, where he had the opportunity to taste the Champions League and La Liga trophies.
Real Madrid's performance does not only depend on Joselu, it is true what you said, even if Joselu leaves Real Madrid, it will not have a big impact on Real Madrid because Real Madrid still has other players who are still quite talented, especially with Mbappe who can help Real Madrid in his attack line. There is no doubt that Real Madrid's performance is very good, they can play consistently, but that doesn't mean they can't be matched and beaten. It is very difficult to become a successful team without losing in one season.
It's true what you said, Joselu is very lucky to be able to join Real Madrid because he can help Real Madrid win trophies as well as taste the Champions League and La Liga as you said. Joselu has achieved quite a good achievement because he has had the opportunity to join a team that has a good history. Joselu's decision to leave may not have a big impact on Real Madrid, but his name will be remembered because Joselu was a player who played a big role at Real Madrid.