It's a normal, universal human response to protest when something you're used to is no longer there. Even though I don't share the outrage, there's nothing 'current year'/particularly contemporary about it.
If you were using a free product with limited history and expected not to lose history then I have exactly zero sympathy for you. Even if the free product you were using changed their terms.
I don't use slack outside of work, so nothing from me. Just sayin' how people are so easily outraged w/o really thinking about their needs and technologies. I have no sympathy for those slack users either, cheers.