One question for the OP…
Is the old Gloria sung with the old (pre-2011) words? If so, then it is now invalid and must be changed - in fact the change is long overdue. That doesn’t, however mean that any new setting with the right words is a good one.
My church changed the Gloria melody and shortened it. The melody is jagged and it just doesn’t flow as well.
We can’t tell from here how “bad”, or otherwise, the new melody was. It may simply be a more modern setting which you don’t like because it’s different, and may learn to like eventually, or it may be one of those awful syncopated settings which are hard to learn, hard to sing, and seem to contradict the words, rather than reflect them.
The Gloria was my favorite part of Mass. It could be sung with gusto and my heart felt like it might burst.
I empathise. When a parish has a familiar and tuneful Gloria, played week after week, then it can be the part of the Mass where everyone sings heartily.
I went to a different parish this morning and they sing the Gloria the way my church used to.
It may be that the old Gloria, and the whole setting for the Mass, is one endorsed across your diocese. The Bishops sometimes do this to assist the singing at Mass by having a choice of settings used across the diocese which are both familiar to all parishes in the diocese, and of guaranteed quality.
Your new Gloria may be approved by the diocese, or it may not be. If it is, then I think you have no grounds for complaint.
In my diocese (of Adelaide, Australia) there are several musical settings
approved by the Bishop. Nevertheless, I know of three individual choirs which would rather compose their own setting, and inflict it on the parish…
With the updated English version, the musical settings we used for the Gloria were clunky and disjointed compared to the previous translation. Recently, my parish have started simply reciting Gloria, which I would prefer at least until better musical settings become available.
There are some good current settings, but I agree with the principle of critically evaluating a setting, and not assuming that just because it has the right words and some music that it must be suitable. Simply reciting the Gloria while you choose the right setting seems to be a good approach.