The best — maybe the only? — real, direct measure of “innovation” is change in human behaviour. In fact, it is useful to take this way of thinking as definitional: innovation is the sum of change across the whole system, not a thing which causes a change in how people behave. No small innovation ever caused a large shift in how people spend their time and no large one has ever failed to do so.
In the best case, there is a dialectic at play here: the product itself and the way people use it should suggest new ways of articulating the value — and refinements to how we communicate the value should lead to principles which clarify decision-making around product features and design.
Just as much as our job is to build something genuinely useful, something which really does make people’s working lives simpler, more pleasant and more productive, our job is also to understand what people think they want and then translate the value of Slack into their terms.