I also own a Canyon Grail (the alloy one, so no weird handlebar) and it's pretty capable for fire roads and some singletrack. When it gets really rocky and rooty though I find myself having less fun simply because the riding experience becomes so jarring and rattly. It's also way more fun to climb on (as in you actually enjoy the climbs as opposed to just doing them to get to the downhills) compared to a mountain bike. Where I live I have to ride ~7 miles each way to get to the trails so it makes a lot of sense as my one off-road bike.