Thiem is younger than Nadal, so you are basically confirming what I am saying, that it cannot be attributed to age alone.
Nadal won two slams that year, Federer had lost to him the last time they played at Wimbledon, yet he did what he was capable of doing that tie break.
It seems to me that there is a theme among Federer fans to try to downplay what happened at W 2019 as much as possible. I know Federer wasn't at his peak, you won't hear me say he was, but to say he lost a match was the longest final in W history going 13-12 in fifth because of his age alone is shying away from facing the truth....and the truth is, a big part of why he lost was because he blinked when it mattered most.