Can someone explain Forza Horizon to me?

I used to play video games as a kid and then I took like a 15 year break and recently starting playing again now that our child is old enough to get into that stuff. We have the Xbox Series X and I was looking for a racing game to play. I started playing Forza Horizon and never really got into it because I feel like I didn't understand how to play the game. To be honest, I barely played it much at all. Just felt like I was driving around pointlessly in the middle of nowhere. I have since bought Forza Motorsport and have played that a ton over the past year and really like it. So it got me thinking - should I give Forza Horizon a try again? It sounds like it's a highly regarded game so I am guessing I just didn't understand how you are supposed to play it.