This is way off base. Like, actually, completely off base.
Comparing the driving model is pointless in that, one person will prefer another and also you can basically completely change the way Forza handles by adjusting assists. On top of that, you can change the way the individual cars handle even more because every vehicle in the game is subject to some decently robust car tuning options. On top of that, all of the said cars in the game will handle differently on the road and off the road. So, going back to that statement, which driving model is that you want to compare? Fully assisted? Fully UN-assisted? Un-tuned? Street race? Rally or completely off road race? Somewhere in the middle ground? As it stands, there is MUCH more to consider from a driving standpoint and that is not even remotely arguable.
This leads to the other point of Forza having more even IF it wasn't an open world racer. If you were to be lead from race to race in a tour mode, the races consist of a wider variety of racing types. Forza has a wider variety of car types as well to get a feel of the top end and bottom end of the driving world. There are city circuit races, rally races and off road races with some combining the types. There are in game challenges that compare your scores/times/drifts etc with others on your friends list or in your club. There are online races of all of these types on top of just for fun modes like infection or king. There are straight up co-op racing challanges. As mentioned earlier, there is a full blown car upgrade and tuning system for all of the vehicles. There is a marketplace for you to find and apply designs for your car as well as a livery shop for you to create your own. There is quite a lot of "strictly racing" in Forza. There is also quite a lot of other stuff in the game as well with no detriment to its driving.
It certainly holds a candle to Driveclub. For all intents and purposes it is Driveclub that doesn't hold a candle to it. The game, for what it is, is sitting at 75 on metacritic, which means it is a good game. Forza is sitting at 85 or some shit. It deserves it because it does what it is supposed to, driving fast cars around beautiful locales, at the top of its class. It also does more than that. It is easy to see how the game would draw ire for its lack of anything but straight driving, especially being released so close to Forza.