I'm wondering how one knows that the mass one attends is done according to the rubrics? For all I know, I may not have attended a "true" mass for most of my life. Some things false are easy to pick up, but the subtle changing/adding/subtracting of words are difficult to know (and, sadly, almost expected).
Most people don't know. Its things like the priest genuflecting at all the times the rubrics require. Or like not having extraordinary Eucharistic ministers habitually at every mass, which is an abuse Rome instructed the Church here to stop several years ago. Or that only the priest should purify the vessels after communion. Or that extraordinary ministers should not all be standing around the altar taking communion with the priest. Or altar boys, lectors, and deacons standing for the consecration. Or that all communicants, who do not receive kneeling, should make a sign of adoration immediately before receiving communuion, either a profound bow or genuflection. The list goes on and on.
Most people don't know, and they claim you are wrong when you even bring up these facts.