Well, lets look back. First consideration is that the game doesnt factor in durability, so we gotta toss out real world and look at the game mechanics.
What do rally monsters have? Speed and nimbleness. Seriously good levels of it. The part catching people off, myself included is that to succeed with them, especially with a wheel, requires a different perspective on play and unique tunings.
Complaints about skinny tires. In rally, skinny tires, especially the fronts is extremely important. The road media is the traction limiter, not the rigidity of tire wall. Not going to pull high G on sand. So you need a narrow tire on steering to give it a longitudinal contact patch so it can bite in. Then wider rears because of reason rally cars drift. Oversteer it as front understeers to push yourself in as inertia tries to slide you out. It is less of a drift, more of an orbit. You are already sliding and trying to counter that.
As for “better”. Grain of salt, the speed can throw off perceptions. Try in actual race. Rally monsters are cannons on the launch. But perhaps vs tuned. Are rally monster dirt tires not as good as the tuning ones? Thinking… Rally monsters defaulted to a dirt tire dont get the ice tire conversion?
Tuning… The 959 is insane, but in addition to narrow front, wide rear, they need stiffer back suspension to keep it planted. It has been the car I have been fighting with to win the cross country championship. Took a bit, but is a powerful beast now.
So I do suspect this has to do more with the current championship. Why do they suck? Well rally monsters are specific for rally. Asphalt and dirt roads while also being road legal. High speed racing. So lower profile tires, lower slung and semi stiffer suspensions. As such, they lack critical features for cross country.
Doing really rough roads or xcountry? Unsprung weight. You need a tall tire and lower pressure to dampen that. You need the ground clearance to not bottom out. Only three cars are suited for rally monster cross country. The Festiva I think it is (the stockish rally one), the Subaru Impreza, and the 959. They are the only tall clearance, tall tire cars to keep it drivable on the harsh and rough routes it has.
I challenged myself with the 959 hybrid swap to win the champ. But if the ford I am thinking might be the best bet. My 959 was 70 percent rear. Built more like a lancia. It is too light in front to have too much bias there.