You are not alone but MS has market share and easy reach with 365. Slack (as an example) is a much better product but MS can afford to be lazy. Hopefully when Slack releases SIP support it will be forced to improve.
If you're a decent sized organization, you can pay $12.50 per user per month to Slack for a messaging service, or you can pay $20 per user per month to Microsoft for Outlook, PowerPoint, Word, Excel, Access, Publisher, Exchange, Sharepoint, and a messaging service. If you just want messaging then you can pay $8 per user per month, and they'll throw in Exchange, Sharepoint, and a terabyte of cloud storage per user on top of it.
I don't think it's possible for Slack to be better enough to justify that kind of a price difference.
That's probably true for cheap labor, but ~50% of developers I know will try to switch into other teams when they are forced to use Teams because it's that annoying. When you pay somebody thousands of dollars each month, paying an extra 12.50 to make him not look for a different job isn't really something you should need to think about a lot.
On the other hand, a knowledge workers like a mid level software engineer can easily cost a business $100 an hour in salary and costs. If Slack can save employees 8 minutes a month then it's a net win.
I dont find teams to be perfect, but I find slack to be overpriced at $15/user. Happy to use Teams as part of my $15/user license that comes with email, excel, PowerAutomate, etc etc
