That would be a passion project. I find it hard to conceive of Teams as a passion project, except possibly by people who have a passion for hating the world.
There are businesses running on software that makes Teams look like a paragon of performance, stability and user-focused UI/UX.
Those (probably) aren’t trillion dollar businesses.
I've used much worse, almost always enterprise software.
That doesn't excuse Microsoft, but ultimately I just make sure my personal life and my jobs stay as far away from their software as I can.