For meetings, calls, screensharing, and scheduling it's superior to Slack in every single way. Written experience is worse though. If only Slack spent a month writing a "Schedule a meeting with those people, and add the meeting with a link to everyone's calendar" feature, they would be on par.
One reason Slack maybe doens't, is nobody actually chooses Teams over Slack because of feature set. They choose Teams over Slack because it's "good enough" and included with Office360 which they already have. Meeting Teams feature set may not actually get Slack any more customers at all.
We do use Teams and Slack, Teams for scheduled meetings and Slack for everything else, just because Slack's scheduling is non-existent while something great comes out of the box from Teams (and yes, also because we get it "for free" through O365, and wouldn't be paying for Zoom). We wouldn't have to deal with Teams if Slack upped their game.