Totally agree - Rocket.Chat is way better than Slack for the simple reason that you can have your own, under your control. Also, it can integrate the Matrix.org messaging open standard. Here're a couple howtos (pick the one that better suits your situation) to set up your own: https://www.maketecheasier.com/install-set-up-rocket-chat/ (disclosure: I wrote this one) https://oer.nz/rocketchathowto
Welcome to the community - and great to see you thinking about the implications of these *open values*... I've been working on that evolution for a couple decades now - the key thing is not ones state in the transition - it's ones intent, as demonstrated by taking the principled - not the expedient - route. I wrote this about it: https://davelane.nz/nethui-insight-open-about-intent
For the record, some of the tools you mention above, aren't as open as they'd have you believe: Slack and Google Docs (and others, like Github, who trade on "openness") are fully proprietary, despite building themselves on top of open source technologies. It's important not to succumb to "fauxpen", and to point it out when the moneyed corporations try to cash in on (and corrupt) open.
Totally agree - Rocket.Chat is way better than Slack for the simple reason that you can have your own, under your control. Also, it can integrate the Matrix.org messaging open standard. Here're a couple howtos (pick the one that better suits your situation) to set up your own: https://www.maketecheasier.com/install-set-up-rocket-chat/ (disclosure: I wrote this one) https://oer.nz/rocketchathowto