The problem is that this is not the first time Neymar has been injured and it is quite serious, he has had repeated injuries and that is what is worrying when he returns he will be different from before. There is indeed a record where he did not decline so much when he returned from injury, he only needed a while to find his game again. But still that does not guarantee that the same thing will happen to him after he returns from injury now.
I agree with you, that this is a different case, when the players you mentioned returned from injury at a fairly young age, so with a younger age they usually recover quickly and also quickly return to their best performance. But now Neymar is over 30 years old, that is an age that is considered quite old in football. Even some players who are not far from Neymar's age have now decided to retire.
Age does affect a player performance, especially since Neymar has a reputation for frequent injuries and has had to undergo surgery several times, to find his best game again certainly takes a little time. From his social media uploads, Neymar looks focused on undergoing physical training, and seems ready to make a comeback to play the new season with Al Hilal. The Saudi Pro League is not very competitive and also does not rely too much on physicality, unlike the top European leagues, so I think it will be easy for Neymar to find his best game again.
So far, Neymar has only played for Al Hilal a few times, and I think Neymar can be an important player next season. Indeed, without Neymar presence, Al Hilal was able to go undefeated throughout the season, most likely with the return of the Brazilian star Al Hilal can retain the trophy. Statistically, Neymar has only scored one goal and three assists in five matches for Al Hilal, we must admit that it is not at all comparable to the budget spent when recruiting him from PSG. It is possible that if injuries continue to haunt him, retirement is the path that Neymar is forced to choose.
He could be an important player when he comes back from injury, I won't deny this because anything can still happen. But will he continue to play without getting injured again after he comes back? Well, that's a question that will be difficult to answer, because we see a history of very frequent injuries, even though it's only a minor injury, it will still make him rest. Al Hilal has also actually shown their disappointment with Neymar, because he didn't make much of a big contribution to Al Hilal's game even though they had spent a lot of money on Neymar. I don't know if Al Hilal will take the risk of keeping him after he recovers, or they will sell him soon. They can also play well without Neymar, so I think they can also make a decision, because they also have a squad that is capable enough to compete in the Saudi Pro League.