Even when Modric played for Real Madrid last season, he wasn't prone to injury, so I believe the same scenario could likely happen to him at AC Milan when the new Serie A season starts this weekend. Since Modric is getting old, AC Milan shouldn't allow Modric to always play full time; they should prioritize changing Modric in the second half so that they can limit Modric's chances of getting injured.
Modric's age certainly impacts his physical strength, and I don't think Luka Modric is capable of playing full-time. He'll likely only be a substitute for AC Milan. Because of this, I don't think we can expect much from Modric's contribution to the team next season, even though he's still very good. Without a strong physique, he won't be able to contribute optimally.
AC Milan has indeed made many changes to prepare for next season, but I still have some doubts about their ability to compete fiercely for the title. I think the arrivals and departures of several players have left the team unbalanced, especially in midfield.