Choose your customers.
I wrote a simple exporter using Slack api. It archives Slack from position of user, almost everything (like attachments).
But I'm not publishing it on GitHub because I don't want more people to use it, and don't want Slack to block mass api calls, and don't want slacks admins to know I written it and use it.
If you're using it personally, the limits on message counts are made quite clear. Exceeding them makes export difficult or impossible without paying. So don't exceed them.
A huge chunk of Slack's value prop (after decent UX) is exactly the fact that they have all of your communications. No chat admins, servers to manage and back up, or networking hell to orchestrate non-text content sharing in a multiparty way. Also makes corporate folks who pay for it happy as they have pretty good auditability/retention controls--not perfect, of course, but better than a truly p2p/federated solution, and again: no infrastructure management needed.
You don't have to be happy with it, but those are features, not bugs, and are valuable to many.
You also just, y'know, don't have to use Slack. Nobody is putting a gun to your head. If the hill you want to die on is "I won't work for any company/team that uses this chat platform", well, that's your choice (hell, there's not even an argument to be made about ubiquity making it a false choice; Slack has plenty of competitors, both paid/hosted and FOSS/federated, in active use by big companies). But don't pretend that a lack of local history or easy export is some sort of highway robbery or hostage situation.
Are you just trying to be infuriating?
What are you talking about then? All of my communications are either personal or employment related, almost by definition.
As others have said, this 'Standard Export' doesn't include direct messages and private channels, so there's still some amount of 'hostage taking'
I mean they are already giving you the oppportunity to use a limited version for free, you can't expect them to give you one of the most useful features imho when you are just using their resources and infrastructure in exchange for nothing; it doesn't make any business sense.
If I'm a non-paying user of Slack (or whatever other SaaS with a free tier) I am not entitled to anything whatsoever, I'd be grateful for the fact that they allow me partial functionality at all.
Personally, I would just call that normal / decent behaviour. Alone, it doesn't mean you deserve a ridiculous billion dollar evaluation
"Well deserved" describes the outcome.
So you might say the outcome is well deserved only if decent behavior comprised the process.