Seriously. Oh, good, now it's only 4-5x as large as it has any right to be, even allowing for modern software bloat...
Such is the nature of slightly optimized Electron apps, T-Mobile Digits Desktop app is a similar resource hog.
Using the browser based version often is less resource intensive.
Tried that, they actively employ darkpatterns to coerce users onto desktop apps. I even asked them to stop asking for an app install on their links that you open from inside the webapp and they told me to get stuffed and use the desktop app.
Yea, I use Matrix integration when I deal with Slack, that way I have my choice of client and there isn't any code of Slack's running on my machine.
Strange, after declining message about "native" desktop app, I've never seen it again. No other issues as well. Firefox 69 on Windows, one paid and one free workspace.