Let's forget about his age, Joselu is a good player but you guys forget something about how Ancelotti has been rotating his players. Since before now when Madrid hasn't gotten Mbappe let's say since the beginning of last campaign, has the coach been showing any sign of giving this guy Joselu a better opportunity? He always sit on the bench or sometimes he plays Joselu around 80-85mins just for him to kill the time, sometimes Ancelotti doesn't even play the guy so what's the assurance that he'll have a playing time (base on swapping the playing) now that they have Mbappe? To me Joselu is just there and there's no special reason for him to be there, if Ancelotti wants to do any sub he can even bring in a defender or a midfielder instead of Joselu.
Ancelotti did not give him a chance to start even after his goals in the semi-final against Bayern, so it can be said that Ancelotti is not changing his working strategy and there will always be a place for Joselu on the bench. Moreover, with the arrival of Mbappe, this situation will worsen, I doubt that Mbappe or Rodrigo will be on the bench. But apparently Joselu is happy with this, he goes on the field for twenty minutes, scores several goals, but he plays in Real Madrid, everyone makes their own choice.
A player who performed very well in a match and that player scored a goal in an important match to win the team is definitely not the manager Ancelotti to select him for the next match considering this one match. Ancelotti does a lot of planning before going into a match and the players who are right with his plan for that match get to play in the eleven for the next match. Since Real Madrid's starting eleven players are doing well regularly, Ancelotti will not want to spoil the good balance of the team by leaving out any player from the starting eleven and giving another player a chance. Even if Joselu is at Real Madrid next season, he will definitely not get a chance in Real Madrid's regular XI.