Why is multiplayer so popular? Serious question.

Last COD I played was MW2 (original). I just picked up OB6 on gamepass and I was so excited for multiplayer (all the hype).

I got into it and I found it super confusing with the menu and the games were just “old school arena shoot’em up” games. Like 6v6 and capture the flag. It was like playing Halo 2 in 2004.

Seriously, am I missing something or is this really what multiplayer is like in COD?