Kudos for at least trying to address this, MS should hang their head in shame, this is not the hardest problem to solve these days. If we could do it in 1995 they should be able to do it 30 years later.
So, what am I doing wrong? How do I get the authentic Teams user experience that everyone else here seemingly has?
I now use Slack, Zoom, Google Workspace etc. and don’t enjoy the experience at all. It feels low quality and messy compared to Teams.
I don't believe you.
Making App integrations for Slack to basically anything is pretty close to a joyful experience, the rest of it is comparable to other chat systems perhaps, but are you really telling me with a straight face that developing applications atop Teams (that do more than just plug other Microsoft things together) is actually a superior experience?
I get that opinions are subjective and all that, but so you understand: I'm having the same reaction as if someone said to you that contracting gangrene is preferable to a walk in the park.
As for your reaction: if your experience is so different, a useful attitude might be to ask why you have such an absurdly negative viewpoint.
To tell you the truth I always assumed it was because Microsoft didn’t really care about chatops or any integration that was not within their ecosystem (or a website). The experience is consistent with that viewpoint.