My problem with the pacing was chapters 12, 13, 14, and 15 were all just a big block without any story or significant change in environment. I stopped playing my first night on chapter 14 since nothing was really pulling me to push forward and stay up late. "when does this part end? I'm pretty sure I've been in this jungle/pirate city/etc area for the past few hours. WHY?"
I liked the ship graveyard from 3. Didn't feel long at all to me.
I'd rank them 2>1>3>4 for pacing.
What did you want to learn about the island? That was my biggest and only let down with the game, since the island lacked any mysteries. I kept making theories about what twist could happen but those never came.
Yeah this was definitely the low point of the game. Either side of the tower collapse, confrontation with Rafe and the flashback (from waking up on the rocks in the storm to when you find the 10 dead founders) the game got repetitive at points. Mainly because it was the same environments, puzzles and encounters over and over again for a bit.
I think if those chapters were cut short and instead there was an extra destination before Madagascar the game would be a lot better in the eyes of people who are doubting it. If the puzzle in Scotland led you somewhere totally different like a desert or anywhere which looks different to a jungle then that would have been good. Solve some puzzles there, enjoy the varied environment then get a clue which leads you to the volcano jeep trail. That would add an extra couple of hours and they could remove some of the repetitive island section in its place.
I hated the ship graveyard in U3. That's by far the worst section in any of Naughty Dog's last four games. It felt like such a waste of time, nothing even happened there, it was just filler to make to the game longer. The story didn't want us to go there. It just wasn't important. It was a drab environment and some of its encounters were annoyingly hard.
Pacing ranks 2>4>1>3 for me. While 4 does get repetitive at points I think its still paced well because those bits are split up by action pieces, story and exploration. Also the early game up to the boat flashback and the late game after finding the 10 founders was perfection in terms of pacing.
I just found the island bit extremely interesting. I really wanted to know what happened to the pirates and why. Yeah there was no twist but it was interesting enough, and it was more about the characters.