To nitpick here: many tenured professors also use Slack, email, alerts etc. There's also often an (implicit) expectation that they can get stuff done in the eve

To nitpick here: many tenured professors also use Slack, email, alerts etc. There's also often an (implicit) expectation that they can get stuff done in the evenings, on weekends etc. (e.g., paper reviews, grants, references, etc.). So I don't think it's quite as easy for modern-day profs to just 'shut [themselves] from the world'.