This thread from Jonathan Courtney of AJ&Smart was an interesting spark I hadn't considered before:
Slack's tagline is literally "Where work happens" and for many, many organizations, that's true — for better or worse. I confess that I hadn't considered the "default screen" observation for myself, and on reflection, I'd agree with it. It's very easy to use it like social media. We may have wandered into Slack, uncritically bringing our previously-email-borne work with us.
Of course, it depends on the kind of work you do and the services a company provides. Should Slack be where work happens? It's likely where the bulk of communication — discussions, decisions, announcements, clarifications — happens, but is that The Work?
In the world of knowledge work, it makes sense that the exchange of information is a significant part of one's job. And yet, there's a sort of clash of clans between Maker & Manager.
For makers, work is a craft, it's generative, and it means making new things in tools like Figma, Miro, github, JIRA, Excel, etc. Manager work is (ostensibly) about building coherence on behalf of the organization. I suspect that a lot of the frustration attributed to email & Slack is the inherent conflict between the two types of work in addition to the schedules, tools, etc.
Of course, most of us have at least a few responsibilities in each camp — which only exacerbates the issue. There's Work and there's Meta-work: the work I'm there to do and the work that I need to do in order to do the work I'm there to do. In any team, there are a hundred tiny tradeoffs between focus ("just let me do my work!") and fragmentation.
It's a corollary to Tesler's Law where the distribution of work in a system is as important as the quantity of work. There's no getting around the work of "talking about making stuff", it's just a matter of how integrated (or disintegrated) the making-talking workflow is.
* * *
On a related note, in the past few months I've had a few discussions with different folks on collaboration, specifically that collaboration can have different meanings and implications within a team. Does collaboration mean:
We do everything together (which means lots of meetings and little asynchronous progress)
I let you brainstorm with me at the beginning
Being in the same room/meeting, but I do all the doing & talking
I ask for your input throughout the project and I incorporate it (lots of frequent communication)
I ask for your input and I evaluate it, incorporating what makes sense in light of the whole
I ask for your blessing when I'm 98% done, but don't plan to meaningfully incorporate it
I inform you what I'm doing (siloed, eventually divergent processes & outcomes)
Each of these are a function of trust, clarity, candor, and capability (among other factors, I'm sure).
* * *
Coincidentally, Crema is re-evaluating some of its longest-used tools in light of how we currently operate and what might improve. We've bumped up against the same challenges for long enough that there are new options on the table — and we have a few new ambitions that these old products can't support. Much like Jonathan above, we're in a new spot. The mental model for the organization is a bit different. Before, certain products weren't necessarily the problem, but they weren't helping; tools are important, but they can also be distractions. These 
will allow a better distribution of work for the company we are today. To get here though, we've had to learn and decide what The Work truly is.
