When is being more efficient at anything a bad idea? If you can get your day job done in 2 hours vs 8, maybe you can argue for a raise or the ability to work from home.
When it drives people to stress, burnout, obsession, losing connection with family and friends, and so on...
In other words, today...
I'm suggesting to work more efficient as well as work less hours. Then you have more time to spend on relaxation and the things you want to do. That is how this modern society should view work, but we don't
So while already "being more efficient at anything" is not bad, the idea of "being more efficient at anything" can be a very bad idea, downright to killing people...