It was fun for a while, but, I don't know. It's old school. Not saying that's bad, but the demographic they're aiming for doesn't play split screen as much. That and there's like 5 days until release, I doubt that they'll change it. Yeah, you could do a patch afterwards, but again, I doubt it will happen.
Dude Halo split screen is literally a staple of the series. Custom games is the shit