Nothing comes close to iRacing for racing real people. There are races going on at any time of the day / night, and their licence, iRating, and Saftey Rating systems help weed out the wreckers and group you with others of similar skill and ability.
While iRacing has the perception of being very expensive with its membership fees and paid content, you can actually race quite cheaply if you're smart about it. For example, a few times a year you can purchase credits for 75% cost. The you can use those credits when membership renewals go on sale for 50% off; so effectively you're only paying 25% for your annual membership. And you can also use those credits for buying car & track content; which if you buy in bulk give you an additional 25% off, or effectively 1/2 price. Plus all you have to do is run 8 races in a season and you will get iRacing participation credits, up to $10 per season. So that's another $40 per year you can save.
Bottom line, you can run iRacing for only a few dollars per month if you take advantage of all their deals / sales / incentives. And if you're good enough, you can join a sponsored team and race for free / possibly make more money than you spend on the sim.
So really, there's no excuse not to join iRacing.