This is not, mostly, my personal anecdotal experience these are my observations of the "way it works" for many people throughout the industry, especially those

This is not, mostly, my personal anecdotal experience these are my observations of the "way it works" for many people throughout the industry, especially those working at startups. Notice that I said nothing about working outside of the typical 40 hour work week and yet you immediately took my comment to be concerned with that. Absolutely the core problem with slack is that it makes it easier for people to be inconsiderate of other's time by making synchronous communication the norm. Slack normalizes the model of everyone communicating synchronously all the time and everyone interrupting everyone else's work in order to communicate, which is corrosive both to productivity and the overall office environment (for the reasons I outlined above). And yes, there are ways to "use slack better" but the problem here is that most tools encourage a natural pattern of use, and if that pattern has a severe negative impact then using that tool will tend to have a negative impact on work as well, on average. See also: using gotos in code or writing readable Perl programs. If there is a "correct" way to use slack then that should be the default, baked into the software, and it should take work to use slack incorrectly. Unfortunately, the exact opposite is true, using slack well requires an uphill battle. People aren't complaining about slack being impossible to use "correctly", they are complaining that it's an uphill battle to do so.