It has search, it's just very basic. Only searches for exactly what you put etc.

I remember Slack's search being equally crap when I last used it a couple of years ago.

sounds exactly like slacks search, except slack also doesn't find exactly what you put in sometimes... (think the indexing isn't very fast because sometime a day old message is impossible to search for)

slack search has been awesome for me. if you want exact search, put it into quotation marks.