I don't see the "decay" theme. You are concentrating on one thing only, overall there is just change, so yes, what was has to go and is replaced. The age of hum

I don't see the "decay" theme. You are concentrating on one thing only, overall there is just change, so yes, what was has to go and is replaced. The age of humans replaces what came before in Middle Earth. That "decay" interpretation would just as well to our earth: The old has gone, "decayed". You misinterpret change just as in "Today's youth is the worst generation", a theme that can be traced through history.