katheriin
Others mentioned Mattermost, Discord, but really, there are so many viable options out there. See this list of 25+ alternatives for example: https://fleep.io/blog/best-slack-alternatives/
From cloud-based to self-hosted, open-source and commercial... As long as they integrate with the tools devs use, there will be devs who use it.
How to Improve Team Communication: The Ultimate Guide
25 Best Slack Alternatives for Team Chat – cos Slack may not be optimal for you
Anyone who does not want the group chat experience can be included in conversations via email.
Currently, that does mean getting all messages via email, and not @mentions (nice idea, worth considering for Fleep's product team). But idea is similar:
Full disclosure: I do work at marketing in Fleep :)
28 Best free software downloads of 2016
The Need for Innovation in the Project Collaboration Space
Top communication and collaboration tools
Show HN: Fleep – Slack-like messenger that also enables chat across teams
Sort of like - I'll send this piece of information out, and maybe I'll get something in response. Maybe I won't.
It's not a to-do list protocol. In fact, as Paul Graham has put it, it's a disastrously bad todo list (Source: http://www.paulgraham.com/ambitious.html)
It's not a messaging protocol - email was never built for conversations, which is why conversations over email often get clunky, confusing and finding some piece of information later is near-impossible.
No wonder people just plain don't like email as a communication method. It was invented in the 70s and it was intended for much lower volumes (Source: http://www.techworld.com/startups/skype-cofounder-jaan-talli...)
The thing is, most 'email killers' like Slack are closed systems and thus have no shot at replacing email - the reason why email has persevered is its openness, how it is the lowest common denominator in online communications (ahem, 2,5bn users worldwide).
Instead of a new open protocol, Fleep (https://fleep.io) has built a messenger that relies on the email protocol by integrating with email seamlessly. With Fleep, you can send messages to anyone who has an email address - if they're not a Fleep user yet, they will receive the messages as normal emails. As a Fleep user, however, you already get the improved conversational experience of emails.
(Full disclosure: I do work at Fleep and I absolutely love the product, the ambition and the ingenious approach our founding team has taken to merging IM & email.)
Funderbeam Launches the World’s First Startup Marketplace, Exciting Tim Draper
This is where Fleep comes in - a messenger that works with email, too. You can include anyone in a conversation with their email address, and if they're not a Fleep user yet, they can participate in the conversation via email. Fleep: https://fleep.io/
(Disclaimer: I do work at Fleep, and I love it :) )