I don't know what it is, but races in FM (and similarly in GT) often look more like track days to me rather than competitive races. There's little sensation of cars being driven close to the limit, of being thrown around the track. It's like the drivers in FM (and GT) are nervous about scratching their paintwork or getting black flagged my a marshal. If you've ever been to a track day you might get what I mean.
Contrast Shinnn's FM6 gif of FM6 with one of SunhiLegend's from DC (and don't fucking dare see this as a crack in the door to an argument about graphics - my point is all about the
attitude of the cars). The BMW in the lower gif is really being chucked around.
FM6
DC
Track days by necessity are effectively processions with very polite overtaking, cars given wide berths, cars driven nowhere near the limit. I hope T10 try to address this in the future to make the races a little more visceral. They are still fun, but rarely balls-to-the-wall
exciting.