I used to be heavily into iRacing, and still have my rig, but it is a huge time suck to build competitive setups and to get enough practice in so as not to get demolished in a race.
It's fun if you choose a good upper-level series and stick with it, but it gets frustrating when something new comes out and you can't get an official race in at the times that you want to race. Or when physics updates to the car that you've been driving require you to build a new setup for it (or wait for somebody else to post one that works for you). Those factors are the big ones in why I no longer race. For a while, I had a series I could race in where I knew the tracks, there was adequate participation, and the car physics were stable for many seasons in a row, which meant it would only take a few laps of practice to get up to speed and ready to race.
The fixed setup series were nice in that you didn't have to worry about setup at all, however, if that setup didn't fit your driving style, you were SOL. I always felt that if an adjustment was available from the driver's seat in the car (such as brake bias) that it should be allowed to be adjusted, but the fixed series don't even allow that.