Name me a 60 year old rock/metal singer who doesn't. The only one I can think of is Steve Tyler.
I've found that 60 is right around the wall for rock singers. Paul Stanley, David Coverdale, and even Sammy Hagar isn't what he used to be, although he's still very good for his age. But from some Youtube searching, it doesn't look like he's even attempted Dreams properly in forever (they do an acoustic version where he sings an octave lower), and offloads a some vocals to Michael Anthony, who's also showing his age (or maybe he's just not suited to lead vocals).
DLR's vocal quality itself has held up pretty well all things considered (keeping in mind he was never an amazing straight up vocalist to begin with), but the biggest issue at that age is often just running out of steam, which is why live his phrasing is awful, and he has to modify melodies all over the place to require less effort, so the result is bad.
His vocals on ADKOT are very good though, and it's not a matter of post processing (there's no obvious pitch correction on it, so it must be subtle), it's that he can still pull out a solid vocal in a studio environment where he can take his time. I hope they record another album before he's not able to do that either.