Your thoughts exactly mirror my assumptions about this game - Normally I'm all over a new racing title, but having seen the minimal content in the base game, and then having to buy the DLC for more events/cars I decided to vote by keeping my wallet closed.
It appears that I'm not the only one either. A quick look on steamdb this morning shows sales in the first 10 days to be between 20 to 50 thousand which in my mind for a heavily marketed and supposedly triple A title (if going by the price) is dismal. Also it shows that 8 times more people are currently playing Assetto Corsa, a 5 year old title, than are playing GRID.
Now I know that the PC game market is different to the console market, so maybe the uptake on console has been greater, but I have my doubts.
Now if GRID truly has bombed in terms of sales then I'm in two minds about it:
The good bit - it means that people have finally wised up to Codemasters practices, and are no longer prepared to pay triple A money for what is essentially an extended demo version. Hopefully this will give Codemasters the necessary kick up be butt it needs to start producing complete games where further paid DLC is a nice to have rather than an essential component of the game.
The bad bit - if grid has really bombed, then this puts the development of further free DLC, such as the promised tracks, in jeopardy. If you've paid into the season pass already then you'll get what's in the season pass as Codemasters are contractually, or at least morally obliged to provide it, but as far as the free DLC is concerned then the question is why put further development into a loss making game that can't be monetised.
I also think the time of the generic arcade racer is over, unless it brings something new, fresh, and/or unusual to the table. I think these days that people expect and want realism, and that when they drive a Porsche 911, for example, then they want it to behave like a real Porsche 911, and not like a powerslidey Ridge Racer clone from two decades ago.
IMO Codemasters should go back to their racing roots and do what they do best, and that is produce focused racing titles again. I think a large number of us would really appreciate proper BTCC, DTM, V8 Supercars, etc, titles reflecting the current seasons.