Insanely high skill ceiling, which is balanced out by the progression system, which is not very steep at all. A lot of diferent ranks for people of all different skill levels, so you'll always be playing (mostly) people at your own level. Most rewarding for me is not grinding for rank, but becoming better at the mechanics of the game. Improvement happens gradually, but sometimes you just get the hang of something, and it feels like you've instantly jumped to a new level. You start off driving on the group, slamming in to the ball, and go all the way up to a point where you spend far less time with all four wheels on the ground than not.
No other sports game comes close to just the amount of potential for coolness. You can do some insanely cool looking stuff, and pulling off sick aerial moves, dribbles, passes, redirects, clutch goals and what-have-you feels amazing. The only game or sport in existence that constantly makes me go "holy s***!" at the stuff I see, in the pro circuit and in my own games.
There are negatives. Best game modes require from 1 to 2 other players. Their performance and attitude dictates your games to a degree where it becomes nigh-impossible to enjoy certain matches, simply because your teammates are either terrible or toxic. The game also strongly encourages you to use one of about two or three cars, which are constantly present in the market, for which many of your random drops and seasonal rewards are exclusively aimed to. You CAN use any car, but you won't get as much stuff for, say, a Takumi (my car of choice), than you do for Octane, the fan and dev favorite. Also, you really need to want to improve to get past a certain point of mechanical skill. Some things, suchs as flip cancels or air dribbles are not things you can really practice in game initially, so you need to spend time in Free Play or Training to get to a more advanced level.
Small gripes though in a larger scheme of things. I have just under 800 hours in the game, and I play it every day, at the very least doing an hour or two hours of straight mechanical practice. And the game is still ridiculously fun every time, sans the few terrible games everyone has to chew through occasionally. Easy five stars, offers hundreds, even thousands of hours of entertainment.