Not shallow - I don't drive F1 games as it doesn't interest me
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ACC won't really have mods either. I mean it kinda does, but it's not built for it the same way rFactor 2 is. But it will do offline championships really well.
If you're after Le Mans, then narrow it down with this -
Do you want mods and options and flexibility - rFactor 2
Do you want really easy accessibility, but maybe slightly less realistic - pCARS2 (or 1)
Do you want structured online racing, and willing to pay a bit more for it - iRacing