Re: I finished the game. Now what?

Now what? Nothing...

This game has no endgame.

Most of the rewards for grinding for stuff in the game like collectables and special unlock cars are either broken or garbage. 

The online is dead with people just sat in garage in every lobby or afk.

The best thing to do is stop playing until some news comes out. Or join the turfwar discord.

The turfwar is a community based around pvp for this game with a lot of players in discord who invite and race in lobbies with eachother. If you have a crew you can also apply to become part of the turfwars battles against other crews.

There's a thread elsewhere about it in the forums here.

Apart from that there's practically nothing to do when you 100% the game.