Ten minutes isn't very long at all in the sim world. The shortest races I do are 20 minutes (at least on the rF2, AMS2, ACC stuff). You need to leave enough time for something to happen. At least make a pass or two and use some pit strategy. I could qualify at let's say, 6th, and in ten minutes you might finish 5th, 6th or 7th, or worse if you crash. The AI are pretty good in some of those sim titles.
I usually do 30-40 mins with fuel and tires at 3x so a pitstop is warranted. The fun is finding that rhythm after a dozen laps and syncing with the flow of the track. At the end of the race you don't get credits or XP or a free car, you get to finally go to the bathroom. lol
I hope this new Forza can give some good experiences in somewhat of a real race setting and isn't just the 2-3 lap drive around the bricks AI experience. That got really old, really fast in GT7. Plus the Custom Race payouts in GT7 are so unfair, it makes it not worth it. If FM can make custom races with fair payouts and utilize pit strategies (fuel and tire wear), they have a chance of pulling some more serious sim racers into it. To not just do longer races but to have fun with the shorter ones too.