Until people experience a Mass which is really, really ‘off’, they usually do give priests the benefit of the doubt. After all, many of us grew up in the 70s and 80s so we heard and saw some crazy stuff, and as it appeared to quiet down we were just thankful to have priests “Mostly” say the red and do the black, even if we know one priest would always manage to substitute “God” for "His’, or another would change one or two things, such as, “Happy are we who gather round the table” instead of “Happy are those called to the supper of the Lamb”.
But if you only hear the baptismal promises (no other ‘Creed’ of any kind) during the Easter season, if the Eucharistic prayer has words from prayer 2, 3, Reconciliation, plus ad libs from nowhere, “He took the cup and thanked You for Your Faithfulness. He gave it to His family, His Friends and said, Take and drink this in memory of Me, because you are loved so much”, etc., well, then, it’s awfully hard to say, “It doesn’t matter” because yes, it does matter.
It matters because the priest (who does know better, as he after all has the GIRM, in many cases is over 50 or 60 and is not ‘unfamiliar’ with the words of Mass) is being disobedient. It matters because all over the diocese, and other dioceses, other people are able to have full and active participation in the Mass, along with millions, even billions, of Catholics who are praying the same prayers, in unison, in UNITY, while because an individual priest is so certain he needs to make the Mass reflect his own desires, deprives his flock of that participation with others. We aren’t saying the same words, and because of the omissions or the emphases in many cases, we aren’t even having the same focus that is called for throughout the Catholic world. So it isn’t fair, and it isn’t right.
And while I understand an older priest who might slip up (we’re only human after all), or a priest who has one or two little personal quirks which overall don’t really change the Mass, the real danger comes from people taking it as, "because it doesn’t ‘really’ invalidate, it isn’t just something that can be ‘tolerated’, it becomes something that has to be accepted, nay, celebrated.
You get people (seriously, you do) who go on and on to others about how Father X’s Mass is ‘so much better than over at other parishes’. You get them feeling that because Father ‘ditches the rubrics’ that they can 'ditch what THEY don’t like." After all, isn’t it about one’s personal conscience etc?
Does this happen to everybody? Of course it doesn’t. But it happens to some, and it leads to chaos, and quite often to children who have grown up with such leaving. After all, if the PRIEST doesn’t listen to HIS superiors and does what he wants, why shouldn’t they do what they want? If Catholicism was really what it was claimed to be, people would be trying to be as obedient as they could be, but if priests and lay people ignore the rules, laugh about disobeying them because ‘they know better’, no wonder that as the children grow they ignore rules and laugh about disobedience because they, too, ‘know better’. The huge group of ‘nones’ we are seeing didn’t come from a vacuum.