I'm not bored with it yet, I've just been busy, but heres a few suggestions..
Physics:
Their alright, but could use some improvement. I honestly wouldn't mind seeing TDU1's return.
Car List:
Its actually really good, but its also lacking in some areas. No Lamborghinis(I know...) One Corvette, no Maseratis, not a lot of classics, off roaders, etc.
Money Making:
Its well known that after you beat all the championships and cups, its almost impossible to keep making money, (besides the Casino but that gets boring quick) I actually enjoyed doing the infamous 180 MPH in traffic speed race in TDU1, that way I could earn enough money to buy more cars with next to no effort, it may sound silly, but since I had already beaten the game and all I did was cruise and race online, that race was the best thing. It honestly kept me entertained for 3 years because I could beat it easily so I could get more cars to cruise in!
Sticker Shop:
I love the sticker shop, but since there isn't an "undo" option, it keeps me from attempting big sticker liveries for my cars.
Photo Mode:
Seems kind of rushed, I loved TDU1's, and the lack of being able to use a wheel and controller simultaneously(PS3) much like GT5 lets you do, keeps me from doing a lot of photo mode sessions.