Not across all titles no, as PC gaming is more niche than consoles. I've never however struggled to find races in RaceRoom, and while I don't race in it iRacing certainly seems more than busy in terms of its race schedules and pool of drivers despite offering a much wider range of races than GT's Sport mode does.
Just checked, iRacing has 9 different events, all with participants starting in the next 5 minutes, with another nine starting on the hour, etc.
I would also argue that some of the PC titles offer more variety and are more consistent in approach, particularly given the issues I see raised here around the frequent changes to Sport mode, such as BoP, variety, unused tracks/layouts, the now split player base, changeable penalties, etc.