Ronaldo left, then players came to Manchester United, and players left again, but Manchester United's position is still at the same level as before.
Same level as before Cristiano departure, really?
I think Manchester United have been declining and they were not at similar quality level like years ago with Cristiano Ronaldo and even couple of seasons before his return to Manchester United. Cristiano wisely left the club as consequence of internal conflict but perhaps he saw no good future with Manchester United.
Years later, they played terrible and worse than seasons ago, which is unacceptable with an ambitious player like Cristiano Ronaldo. If he had not leave their club, he would have not contributed too much by becoming older and older year by year.
It is natural that Cristiano Ronaldo will not be able to perform the same way he did at 42 years old. With age, playing skills and speed decrease, but the way Ronaldo is playing football at this age is no less than an ordinary footballer. Ronaldo's first wrong decision was to leave Real Madrid and move to another club, if he had stayed at Real Madrid, maybe he could have played for Real Madrid for a long time like Luca Madriz, but he did not stay at Real Madrid and visited several clubs in Europe and finally he returned to his old club, although he was not shown much respect there. At this late stage of his career, Ronaldo may have prioritized his own respect, which is why he did not try to return to any other club in Europe. However, all in all, he is doing well in the Saudi league and it is certain that he will stay there for another two years.