I can't imagine what it'd be like since gender is such a huge part of our society. I think most people would simply be their most primal selves. As long as clothing/behavior kept us healthy, comfortable, and protected there'd be no expectations about what girls and boys wore. I don't think I'd be as worried about my appearance, idek if I would care. Maybe the expectation would be that everyone is neat and well-kept, rather than muscular/fit/strong or skinny/pretty/etc.
I feel like beauty standards would be out the window, or at least completely different. And that alone would have such a huge ripple effect
But honestly I think people would be a lot healthier and happier. Gender norms have a lot of consequences, and if we lived in a world without them... wow. Less depression, less therapy would be needed, less arguments and fights. The possibilities are endless.