Not sure if I'm biased because I've done sport for a good part of my life, but sports definitely builds more than just your fitness or strength. I was part of a sports team for a good 10 years and the tenacity and perseverance it cultivates is something I feel you cannot gain through mere gymming. Sports builds character and played a major role in making me the person I am today.
I don't mean to say gymming doesn't build character - it does in some ways. I'm just an advocate for putting yourself in a bigger playing field for the goal of self-improvement and good camaraderie with friends and rivals alike.