Being able to go back through two years of chats with your wife most likely was never an intended use case for Slack. For a free tier, 90 day retention seems reasonable. The issue Slack has in their pricing, for private use, is that the cheapest tier is pretty expensive. This could be remedied by adding a private tier, for $1 per month per user. I think Slack has put a large number of potential customers in a position where they are asking them to upgrade to a paid tier, but not providing a realistic tier to upgrade to.
I am fascinated by the amount of people who use Slack though. While completely off topic, it an absolutely mess of a thing. It has to be one of the worst UIs I had the misfortune to use. It makes Google Chat look reasonable.
That might exactly be my problem with Slack, and Google Chat as well. I understand the desire to wanting to some sort of threading, but it doesn't work in either programs. Instead it just confuses the interface greatly. Slack is super weird, because you can have a thread open, and navigate around, so the thread view is now completely out of context.
I'm sure it depends on your use case etc., but in my work context I find they function really well.
I did try test some concepts around Slack/Discord threads serving as entire "discussions" for a literary community (so you e.g. post a topic and discuss it in the thread under the topic), and in the end there were a bunch of small pain points that all added up and made it unfeasible.
At work though I find Slack threads to be a good middle ground for having discussions in a medium-large channel with interested parties - everyone can see the main channel message, and those who choose to engage further can post in the thread or opt to receive thread updates if they just want to "listen in"... then if some important conclusion is reached you can opt to send that thread message out to the main channel as well to catch other people up on what was discussed.
Besides the default/obvious channels, we generally seem to have a channel per "team", a channel per "division" (group of teams), and then some channels for "division collaborations" e.g. data science + engineering. Then we also often set up a channel for big new features/projects and invite stakeholders to them.
EDIT: I guess the last type could be what you mean by "topic" - we are a startup so perhaps the number of feature/project type channels will balloon out over time, but doubt we would end up with "zillions" haha. And loads of them would be old and essentially archived.
A lot of the channels become somewhat bloated over time, with people joining because they are interested in keeping up with stuff in a broad context, but have no need to click into each thread and read over everything.
I would choose threaded discussions over PM groups or short-lived channels any day tbh.
I think the problem is not with threads themselves but with Slack's implementation. Threads provide a much-needed way of creating a discussion around a specific topic that doesn't pollute the main channel. In Slack they seem like more of an afterthought than a primary communication tool.
Being able to go back through two years of chats with your wife most likely was never an intended use case for Slack. For a free tier, 90 day retention seems reasonable. The issue Slack has in their pricing, for private use, is that the cheapest tier is pretty expensive. This could be remedied by adding a private tier, for $1 per month per user. I think Slack has put a large number of potential customers in a position where they are asking them to upgrade to a paid tier, but not providing a realistic tier to upgrade to.
I am fascinated by the amount of people who use Slack though. While completely off topic, it an absolutely mess of a thing. It has to be one of the worst UIs I had the misfortune to use. It makes Google Chat look reasonable.