I don't agree that basic functional game design elements are "decline." The number of invincible questgivers is annoying but also is the only reason this game is able to have elaborate C&C and quests more involved than basic point A to point B fetches and escorts like the original had. Also, the only things I can think of that fit what you're describing are the wanted posters, which represent evolving conditions on the island. They actually, literally aren't supposed to be there until their appointed time, the world isn't static. New threats emerge throughout the course of play.
Exploring the forest next to Bengar's farm, finding three scavengers pecking the empty ground, and then after you accept the quest to find the missing guard, and having spent half an hour searching the forest for him, go to the spot you killed those scavengers from before to find his miraculously spawned corpse, is indeed decline. The world shouldn't be static, true. That's what chapters are for, even day - night cycles. Not
that though.
Still, it's true I can't fault this mod for much. It does so many things right though, when it falls short of something Piranha Bytes did right 20 years ago, it leaves a sour taste.