I think OP assumes collocation, and would suggest in person discussion. See the 'sheet of paper is all you need to plan' note. Since they also complain about o

I think OP assumes collocation, and would suggest in person discussion. See the 'sheet of paper is all you need to plan' note. Since they also complain about open office, I think their ideal mode of work is a small team with their own office, caring only about their little silo and not much for what the rest of the company is doing. For some types of work, that is indeed optimal! To me, not having an instant messenger at work would be a great loss. You now either have to come to someone in person, and be way more disruptive - after all you can silence slack notifications, but you can't suppress someone coming to you, make calls - same problem, or do with something like email, where the back-and-forth is much slower.