For several iterations of both the Motorsport and Horizon series the various race settings are pretty lack-luster and not very in-depth.
Sticking with Horizon 5 for the moment, it is great that we can set the season, car types, number of laps/time duration, time of day etc, all that is fine. But what about horse power cap? Drivetrain restriction? Those two alone would complement the current options very well, let alone the many more you could have that would actually make sense for a racing event.
The Motorsport series has these options but does not allow many to stack, very limiting what you can realistically create. Not that the AI can generate cars for what you choose, but the Horizon AI can and we do not have these options.
Also, what is with the Rules of Play options? Seems useful if you want to add a parp noise every time you pass a checkpoint but nothing else.
What about staggered start time trails? What about Joker Laps for Rallycross like events? What about time penalties for ramming? Forced speed limit for a duration as a penalty? Something ACTUALLY useful opposed to turning off gravity or spamming a vuvuzela.
The Horizon series is great fun, but it is so frustrating that any form of realism based event needs to be done multiplayer as you cannot dictate many things for single player, and then you need a group of people willing to build their cars to the rules. Pretty impossible with randoms.