When it comes to the campaign it's as if we're still playing Halo CE due to the level design.
Does Halo 5 have any levels the size of CE's second level?
Point A to Point B wise it might but overall area wise I don't think it does. For the Halo level not only is it long but the areas are large as well. There's a decent amount of openness and there are structures you can go into as well. For Halo 5 the levels may be longer but they're not as open. If anything what makes the levels longer are the increased enemy encounters and there's more to them.
Halo CE was pointlessly open, though.
It didn't add anything to the game. At all.
Do you also enjoy the emptiness of GTAV's open world?
Halo 5 Content Update 2 - Cartographer's Gift