slack notifications are beyond broken as well, so no competition there
I just gave up eventually.
Have you spoken with Slack directly about this? I've brought up several issues to their "Feedback" area and usually have very quick responses for a company that services as many people as Slack does.
Of course Discord has the image problem of being marketed to gamers (and that's fine, because it lets them focus their efforts), but as a tool it is pretty well crafted.