[johnisgood]

I mentioned in my last sentence that as long as it is not mandatory, it is OK, but there are cases where it is mandatory, e.g. at the workplace.

I do not use Slack. I use self-hosted Mattermost as a replacement of Slack, I use IRC, and I use Element (formerly known as Riot.im).

[cannedslime]

Well, you will never get around being forced to use something in your workplace. I would never use Cisco VPNs but I had to install their shitty client in every workplace I ever been on.