Joselu is young and just scored a win goal for Spain to beat Italy in Nations League. However, he is far to be considered as a world class striker. He can improve his skills like Kane did years ago and became a world class striker but I feel he won't be able to do this if nothing really big will change his career.
I am doubtful that Joselu will be able to replace Benzema for Real Madrid as there is big differences in skills and experience of two players.
Is 33 years old young enough? I think you are wrong, this age is the end of a career when footballers are in the final stages before retirement. I think the best age is 25-30 years, that's the best period. Joselu did perform well in the UEFA Nations League 2023 semi-final match against Spain. It looks like Joselu is a good replacement, but Madrid must have another alternative. It could be Kane, Mbappe and maybe Mane.