Many of these decisions you refer to are not made by the individual employee, but by the team lead, PM, or the executives, who are not always very connected to how those decisions affect developer happiness. So getting control of your personal digital life often has no bearing once you enter the workplace with an entirely different set of expectations.

Slack being a public company worries me even more, because there is now an even greater drive for them to make ever-increasing revenue/profits, which usually means keeping people on Slack and active within the client and increasing daily active user / engagement metrics. In many ways there isn't great alignment between a company being productive and Slack's financials; Slack is incentivized to boost revenue even more now, likely at the expense of end-user productivity.