I am a long time TrackMania fan, played back on 2008 and got pretty high on the rankings, then i was forced to stop because the license of my United account was limited back when i bought on the Nadeo website, i missed playing this game and BAM! I saw that Steam got the entire season to buy, then i almost instantly returned to this addiction! (thank you lord Gaben)
You can never get bored of TrackMania, the competition catches you in a never end cycle. You're going to start on the Stadium mode, which is pretty straight forward, beat the time of your opponents and climb the ladder with millions of players, yes i know this isn't an easy task, but it's very much worth when you improve and play with people with the same skill as you.
The community is one of the nicest i ever knew (League of Legends veteran here), for example, when i enter the Coast server, every single person says hello, good game, they even compliment when you get a nice record, i highly recommend this game if you want to make some friends, you'll feel like home!
There's 7 other modes, including Stadium, you can try them all on the Solo play, and you can search if they still have a dedicated server of the mode. I'm a Coast player since when i found back on my days, i loved it more because it's more my playstyle, i'll resume briefly how every one of they are:
*Stadium, it's the first one, arcadish and fast, it's the first door to understand the game.
*Coast it's more like a grip challenge, how to control your car, it's the most competitive of them all in my honest opinion.
*Island gets pretty insane with the Ferraris and their speed! Put the cockpit camera and fly on the track.
*Desert you can handle your muscle car pretty nicely, but in the turns, you better watch out!
*Rally is when i suck pretty hard, remembers me the "ColinMcRee Rally" series, watch your brakes.
*Snow it's one of the funniest, honestly, little cars in apparently toy tracks, Micro Machines anyone?
*Bay, when the SUVs reaches lightspeed, pretty awesome to handle those cars!
The only one Cons i found is, TrackMania isn't very popular nowadays, because Nadeo implemented a FreeZone kinda style, which is, every free player (from TrackMania Nations) can play 2 or 3 tracks, and needs to spectate one because of the FreeZone limitations, this got the game on the ground for many years, but the fun is the same with the United version, you're not a free user obviously, and can experiment all of the modes, try the game, it's really worth!