If u want to attract new viewers who may not even play a certain game, ur gonna want something that easier for them to comprehend. Overwatch is fast and fairly complicated with everything you have to pay attention to. If rocket league was as popular as overwatch itd be the ideal game to showcase like this.
I get your point, but the presentation is so good that, you know at least "The guys in blue are from my team" and you can cheer when the guys in white get Team Killed...it really is that simple.
Only thing more simple to watch would probably be Street Fighter. Literally there's NO games out that are that engaging while still being watchable. Even PUBG can be a slog without the proper shoutcasting.