I checked some of the schedules and they seem much worse than they used to be. Every 12 minutes is fine for maybe the Yellow Line or another suburban route, but it seems that most lines are operating far less frequently, especially important lines like the Brown Line. The Green Line is down to a pitiful 24 minutes on its branches in South Chicago. What happened to make the frequencies so bad?
During the pandemic the CTA lied about service cuts, insisting that there were none. They did this by pretending to run a train or a bus by leaving it in the schedule, but of course it wouldn't actually ever show up. This lead to people complaining about "ghost trains" or "ghost busses" and so the CTA, with great fanfare, announced that they have fixed the ghost service problem. By massively cutting scheduled service. Problem solved