They haven’t exactly gone silent about Merchant Data Corrections. More than one staff member has posted to say that the problem is the tooling used isn’t up to scratch any more (because of scaling, I’d guess), and they need to develop new tools before major improvements can be made. And, rightly or wrongly, this isn’t a high priority at the moment.
Which is a little disappointing, but not exactly silence.
That they don’t reply to many of the “What the heck has gone wrong here?!” posts is probably because these reports should go through the app for action instead, so there’s not much a forum poster could do other than say “Report this in the app”.