A hazy announcement like "I'll be doing more to fight climate change" may indeed be empty virtue signaling that leads to nothing.
But what about a more precise announcement like: "I'll be writing a book on Topic X, which I plan to publish 15 months from now, and I'll be completing one chapter on the 25th of every month until then"? Now we've got intermediate deadlines, and deliverables, and at least the first stirrings of a coherent plan.
Announcements can work quite well, as long as you're willing to commit with enough clarity that your friends and rivals will keep you honest.