I'm convinced the game just wasn't ready last year. The poor reaction to the campaign demo allowed 343 to delay the game with minimal anger from fans because most fans were demanding the game be delayed. You don't skip showing more than half of the game, all of the multiplayer side, forge, and anything else at E3 mere months before releasing in November if you're planning on actually releasing on schedule.
I'm glad you see what they're going for.
As to why it looked like that mere months before it's planned launch, horrible mismanagement, only thing that makes sense. Or maybe COVID just impacted their schedule that significantly.
As to the gameplay side, I don't think that's fully shown yet. Remember this game has upgrades, so it seems there's a new pseudo RPG feel to go with its psedu open world approach. We shall see.
I still maintain to this day that if I can't dive out of a pelican battle royale style during campaign I'll see that as a huge missed opportunity.