You are "most certain" about something that empirical data refutes. Health care costs grew more slowly after the ACA than before it and, in particular, at no point subsequent to the passage of the ACA have health costs grown more than they did during the Bush era.

There are all sorts of things that should have (and perhaps even did) impact prices after the ACA. Not just coverage requirements (which, again: most employer-provided health plans --- which is what we're talking about here --- already complied with), but, more importantly: unprecedented instability in the insurance markets during the almost decade-long concerted effort by the GOP to hamstring and ultimately repeal the bill. And yet, the numbers are right there: health care costs are growing, but they are not growing more than they were prior to the ACA.