Yes, Brian 59...
...you are playing a different game. The gymkhana IS a requirement to move off the first tier. At least on PC, I can't comment on consoles. You cannot advance without completing each of the "skill" lessons and the "competition" at the end, which I got through has fast as possible and with as little effort as possible. After that, as I said above, you can dodge them in the seasons if you prefer.
Regarding vehicle handling alterations and tuning, there are six massively over-simplistic sliders you can move, which you can use to make your car utterly uncontrollable if you like, but none of them allow anywhere near the amount of alteration you could manage even in the original Dirt, let alone a "proper driving sim". Doesn't bother me massively, although I'd much prefer a couple more, but it does put this firmly into "game" and out of "sim".
As others have said, Dirt3 is dumbed down like mad for the console kid crowd, whether they be 14 or 41. I'd probably rate it closer to 70 than 90. Fun, pretty, but far from groundbreaking and not what they advertised (which I never expected it to be, personally).
Available in bargain buckets all over the place for about two fifty and working fine on my Windows 7 64 Home Premium rig. I think I had to use a third-party installer to make it actually work, but may be wrong on that. I've had it installed for so long I can't remember!
Boffin icon because I actually know what roll bars, brake balance, toe-in etc. do, even if Dirt3 won't let me loose on them with a virtual spanner.