As a father of two who has to balance spending time with the family and also occasionally gaming, Forza Horizon 3 really fits the bill by respecting your time, letting you enjoy its various systems at your own pace. You can customize various aspects of your experience such as the driving difficulty, AI difficulty, etc, so you will have an experience that fits your skill level.
There's also a lot of diversity in the environments. The game features Australia, which has a wide variety of locales like beaches, deserts and rainforests. It almost feels like an old Sega arcade racing game at times with all the amazing scenery you'd be whizzing past in whichever fantastic sports car you can pick from over 350 in the available stable.
Eventually you will complete the game but even the ending acknowledges that there's really no end to it....the game is meant to be enjoyed just like that. Feel like a quick race or two? Fire it up and just spend 30 minutes or so on a leisurely drive, or compete with a pack of racers which you can customize in various ways. You can't design race courses (unfortunately), except for the Bucket List Challenge blueprint mode, where you can definitely invent some interesting challenges for other players.
Netcode in this game is superb, just as good (if not better) than Forza Horizon 2's. I haven't spent too much time with coop mode but the one time i did use it, it had a bit of lagginess. Maybe it's been patched out but I haven't gotten to try it since after launch.
Overall, Forza Horizon 3 is the type of game that you just HAVE to buy for your Xbox One. You might not play racing games, but this one will definitely give you a lot of fun things to do even if you don't enjoy the genre. For guys like me who've played so many racing games already, Forza Horizon 3 is a phenomenal experience. It's just a beautiful game that's fun to play, it never runs out of things for you to do, and racing against AI or even other players just never gets old in this one.