We will never know how costs would have changed if we didn't implement the ACA, and cost is not the only metric of success. But it clearly hasn't led us to a place where people feel okay with what the industry costs.
Also necessary to remember the ACA was only passed because of Democratic support in 2010. Republicans hacked away at the proposal before it became law, kneecapping any real institutional changes it had contained, and have effectively killed it since becoming the majority in the House and Senate in 2024. That bipartisan support piece is required in order for anything meaningful to happen.
At a minimum since we don't know what prices would be today without the ACA, prices have risen dramatically in recent years to a point that I think most agree its unaffordable.