it does include threads, and no need for admins
Their biggest problem is that nobody uses them, though.
And since then... nothing. No more improvements. Development seems to have more or less halted since the Salesforce acquisition.
I used irc for a couple of decades before Slack, so was happy with purely linear chat (yeah, I'm also one of those weirdos who likes rebasing in git). Threads make everything more horrible, but at this point it feels like I just have to put up with it.
I like both rebasing and threads. More generally, I hate hate hate the 20+ individual messages on a single topic in a channel. It's just so annoying, threads are great for stuff like that, and give you one target for a reminder/update on whatever the issue is.
And yet, every time I change companies I realise again how much most people just don't threads on Slack.
alternatives:
discord has inline quoting and threads. treads are a bit more visible.
zulip creates a new thread for every message because it prompts you to set a topic, and then you browse the messages by topic.
To be fair, this is hyperbolic. To clarify, small groups within most orgs tend not to use threads in their internal channels AND congratulate everyone on their birthdays. The combination of this irritates me due to repeated notification spam.