Just to state the obvious: if good communication with backers is the goal, the only right way to do so is via updates on Kickstarter, the one and only service where all backers are guaranteed to have an account. Only backers can respond, and if they want to keep something private they can limit visibility to just backers. But if they don’t limit visibility, then people on the outside get information as well, saving everyone the hassle of repeating questions or answering things that were already answered. Moving the bulk of the communication to Slack removed the transparency that Kickstarter projects have by default, hence part of the frustration some people are having.
I get that the team is having to focus their time and energy right now, and that splitting their attention between current and future customers may be more than they can do right this moment, but from my view on the outside, this seems like an entirely avoidable problem.