A thread about one of the newfangled Tom Clancy Ghost Recon games inevitably brought up comparisons to the older games in the franchises. And reminded me of a feature that made an otherwise needlessly frustrating shooter something interesting - the go codes. Used to be you could order your teammates to move around the maps and switch combat roles as they reached way points or on the fly which worked OK. But they did their best when you used a command to make them stop and wait for your order to do something. This made flanking and clearing dangerous areas a game of chess with bullets. It was great.
But somewhere, sometime, this mechanic just vanished. Perhaps no coincidence that the overall quality of the games plummeted at the same time since Ubisoft's AI coders could be replaced with high schoolers starting out in computer programing classes and no one would be able to tell the difference.
What other game features/mechanics have suddenly just vanished for no good reason?