I did the same. Teams on my brand new (in 2019) laptop with 32 GB of RAM had vastly,
vastly worse performance than even the web version of Excel. Slack, when I started using it more than ten years ago, was vastly more usable than Teams is today, or will likely be in five years.
> Surely they could afford to revamp this product and reap the rewards of people not hating using their tools?
It's not a business priority. Management is sold on Teams by integration with their existing services, as well as security, compartmentalization, and so on. They're not sold on "this is a polished product that people enjoy using".
And when you look at the spec sheet, Teams is an awesome piece of software. It can replace Zoom, phone calls, Slack, file sharing and collaboration, and so on. It can even replace e-mail to some extent, though if you're working at a company that's mandating Teams there's a good chance that your company has a strong e-mail culture and people are still going to e-mail you all the time for no good reason.
Anyway yeah, Teams is just the worst.