How is Halo meant to be played?

As someone who grew up playing PC shooters like Counterstrike, COD4, Battlefield etc, I never got the chance to play this legendary series much. With Halo Infinite on Steam though, I'm trying to get into it.

My problem is I don't understand how you are supposed to play well. The bullet-sponginess and slow pace is very hard to get used to. It seems like if it's a 1v1, you point and shoot and maybe get a kill. If it's a 2v1 you die every time.

That said, I just tried tactical slayer and dropped 18-5. With the mouse it felt borderline unfair. But the normal game modes feel gross to play as someone used to other games. Maybe this game is just not balanced for kbm?