sounds like sunk cost fallacy to me
You cook not because you enjoy cooking, but because you want a nice meal at the end.
You work out not because you enjoy lifting heavy shit, but because you want to get stronger.
Its not "sunk cost fallacy" when there actually is a likely positive outcome in the end that makes it worthwhile.
Anyways, I specifically said I'd prefer this sagging of the game to be removed, and for the game to be shorter and tighter. A 60 hour game can drag for 20 hours of no new locations, no new characters, no new mechanics, leveling not adding anything, little story development, and then accelerate the plot and the gameplay at the end. Just drop the sag and make it a 40 hour game. Drop the filler.