The ordinary way changes to a complex law like ACA would be done is thru the legislative process. Common sense fixes that everybody assumed would need to be made given the scope of the aw and the changes it ushered in. So each time a fix is made by the Obama admin the cries of "dictator" reverberate around the right wing sound chamber.
The reason these changes are being made unilaterally by the admin is because every proposal to make the changes legislatively brings an attachment to the bill from House Repubs to repeal ACA. In other words they are blocking legislative remedies with the purpose of being able to disingenuously accuse Obama of being a dictator so all you rubes can jump up and down with indignation.