alt Hacker NewsSandpit should be a personal (often local, if possible) dev environment. The reason people get mad about dev being broken for long periods of time is that they cannot use dev to test their changes if your code (that they depend on) is broken in dev for long periods of time.
Agreed on all points. Local loops are faster and safer wherever possible.
But particularly for devops / systems focused work, you lose too much "test fidelity" if you're not integrating against real services / cloud.