Yes it does, because in almost every case it sucks :) The only one where it doesn't is where it's all indexed by Google (the bad option) or where you index it all locally (e.g. with mu). The second is a slightly less bad option but not by much.
I mean I get it but fundamentally it's not true. Might seem like a nitpick but it's not. If slack search sucks, that's an absolute statement. It is what it is and there's nothing you can do about other than beg a product manager at slack to make it better but they'll likely ignore you.
With email, an open standard, you can just switch clients. Or bypass clients entirely and handle search separately. There are no limits to what you can do.
I find it, potentially forward something and then carry on.
I happen to use an email client with better search and tagging than Gmail.
Gmail is good at this when splitting the inbox, but after that it’s all forgotten (unless, once again, you add a manual filter to exclude such emails)
Email is a standard set of protocols and wire formats. So it doesn't make sense to say email search sucks.
If your email client doesn't support satisfactory search, switch clients. Which you can do because it's a standard, not a proprietary app.