Being unable to mute pings is no longer acceptable for 1 simple reason:

The mia ping has become nothing more than a tool people use to shame and harass their teammates. Easily 90% of the time the ? ping is now used, it is to call out a teammate for a perceived mistake or draw negative attention to that player. But that's not the only ping players use maliciously. Being able to ping dead players has been an absolute boon for the toxic player. Teammate you don't like dies? Spam ping their portrait 7 times so they know exactly how dead they are. And the worst part about all this is that because you can't mute these pings, toxic players will use them to continue to harass players who have already muted them in chat. This is completely unacceptable in the current state of the game; un-mutable pings have given ragers and bullies unblockable power to harass their teammates. How do you expect people to just put up with someone spamming pings on their face at every possible opportunity? That kind of harassment gets you arrested in real life, and the fact that it's still possible in this game is appalling, especially for a company that takes such an outspoken stance against toxic behavior.