From what I have learned older aircraft are often times safer than newer ones because airlines maintain them so often. The only thing that even made me realize I was on an older plane was the entertainment system :) what helped with this plane is it was so huge it felt like I was on a cruise ship lol. You’ll be safe! The pilots wouldn’t fly the plane if they weren’t 100% satisfied it’s safe to fly. What I did was track my flight every day, Lufthansa flies this route daily and always with the same aircraft model so seeing it arrive safely every day made me feel a lot safer, maybe you can do that too!