Sounds like you just played a more limited array of sports. Football is honestly not easy without uniforms, but possible especially if 7v7 or something.

But playing ultimate Frisbee, capture the flag, etc without uniforms is essentially impossible. Remembering who is on your team isn't even the hard part. It's more because you need to make quick decisions and recognize who is open immediately.

So yeah... that's how uniforms work. I would be baffled if they weren't the norm.

Did y'all use uniforms in World War II? No wonder the Germans were able to slice through your defensive lines so easily, you couldn't tell who was on which team.