The real WRC cars look INSANELY grippy on gravel, on both TV cams and onboards, and Dirt Rally makes you struggle way too much, because "lul muh rally 'sim'".
And the most modern cars in DR
are INSANELY grippy on gravel. In order to differentiate the various car classes, older cars get progressively worse grip in what feels like an unrealistic way, but it almost sounds like you're comparing DR group B cars with WRC 10 WRC car grip levels. Also, in a modern WRC car the driver still has to create grip by controlling the weight distribution, using the right amount of wheelspin to sweep off loose gravel, etc; they "throw" the cars around partly to create the grip. Whether that qualifies as "struggle" I don't know, but I'm pretty sure your gravel grip would be worse if you handled them more gently.
So yeah, I do agree that some car classes in DR feel way off in terms of grip, but I also tend to find those the most fun as they require more care with your inputs (first time I tried Lancia Stratos was fun - I didn't get more than 100 meters before spinning on a straight after a slight bump in the road in Finland).
And OT: I've done 3 rallies in WRC 10 career mode with an R5/Rally2/WRC2 class car so far. It feels better with a wheel than previous iterations, like I'm getting the information I expect/have gotten used to in DR/RBR+NGP6/Assetto Corsa. WRC 8 felt a little lacking in that regard, but was great with a controller (f.ex. you can feel the car slipping under braking and acceleration in the Xbox controller trigger button rumble, DR1 doesn't have that, nor do my pedals...). So far so good. The R5 car is easy on the verge of a little boring to drive, but as I recall the real fun starts once you get to the WRC cars.
I really like that you get to manage the tyres over the entire rally now rather than just getting fresh ones every service. You start with a set amount of tyres for the entire rally, then you bring 5 or 6 of them with you for each loop, can swap them around before every stage, you can mix&match hard/soft/rain/snow depending on the surface/weather, and reuse tyres.