I don't like Teams, but personal preference aside, I hate how in most companies I've worked at, there's multiple communications channels. 365 should be a one stop solution for this, emails, calendars, meetings, files, and chat, but in practice a lot of IT organizations also use Slack alongside it. Where I work now there's a split between IT and the rest because the rest uses Teams while IT uses Slack, causing the barrier between the two to increase, especially since designers - who should work closely with development - are on the Teams side of the fence.