If you're debating a lot about communication, you may have a load problem, not a communication problem.
Email doesn't work for this, IM doesn't work for that ... certain personalities are fine with interruptions, others aren't ...
If the real source of your frustrations from not being able to communicate with people is that you just have too much work to do, then debating the best way to communicate is irrelevant.
If a company is rushing on the backlog side of things (e.g. stories and acceptance criteria are incomplete), because they have a fixed deadline for the end of the project, you may say, “Well, get your act together so we don't have to push back on incomplete stories and criteria.” ... except Agile says, “Embrace change, it's okay (even expected). You won't/can't have your act together” ... so, you can't have a fixed deadline.