Yes, the Italian sparkler served isn't the worst thing in the world, but those who know wine will be able to tell the difference.
Are there good sparklers out there that aren't champagne and amazing and get similar scores? sure
Is it a first-world problem? Of course!
Is AA being cheap as usual by cost-cutting the J class experience? As always.
There are people who do like champagne and those who only do it for the name. Nonetheless, the name is a status symbol, a marketing product and champagne doesn't have to be expensive..if AA's marketing team were more intelligent, they could've simply switched to a cheaper champagne but kept it, for the name at least. Now everyone's talking about the downgrade, and even United serves Nicolas Feuillatte champagne in Polaris, and the price is very similar to the Ferrari prosecco. Feuillatte is also what BA serves even in intra-Europe J class...so now AA looks so cheap (even cheaper than before) with this move.

Next, they'll limit the wines to one red, one white and get rid of port/dessert wines altogether. After that, it'll become a dry airline