Again, I think you are focusing on the more able (Judging by your comments you are blessed with a very bright DS).
At one point, when AS s were introduced the then Sec of State decreed no exam should exceed 2 hours at AS.
I didn't do O levels ; I did Scottish O grades but I genuinely think they weren't 2 1/4 hours.
It's not just the length. It's that combined with another exam and the hoops they have to jump through in just that one exam,so they can't settle and rest on one thing.
So, there's an essay question on a modern text, followed by an essay question on a poetry anthology (comparing two poems) followed by a question on one unseen poem, followed by a comparative question on that poem and yet another unseen poem. If you don't think that's a hell of a lot, then I would be very surprised.
I do think - and have always thought - that English and Lit are very demanding GCSEs, involving at every stage lengthy essay type responses.