Since I just had to deal with a Teams issue, I'm going to list some reasons I dislike it. Obviously, everyone's mileage is different and something that bothers me may not bother others. However when people complain about Teams, it's generally because of the following:

• It's slow. I don't care what MS says, Teams is really slow. It is slow to start, it's slow to load content, and it's slow to upload content to, and it's slow to navigate around in. This doesn't mean it's painfully slow, but it's slow enough that I think about it and that means it's too slow. There is no excuse for performance like this in 2025 unless the excuse is you're packing as much telemetry and data collection garbage as possible into the application.
• The integrations are really clunky (and also perform poorly). For example, if I upload a 30 second mp4 file it will go into Sharepoint and be served in MS Teams through MS Stream. Think about that for a second. A video file needed to be uploaded to Teams, shipped to Sharepoint for network storage, then read by MS Streams to feed back to Teams. Just render the fucking file in Teams. This isn't hard. With the way they have it setup, the performance is terrible, the user experience is terrible, and it's insulting that we're being fed this bloated garbage. For context, I'm on a fiber connection and I still see buffering issues and slow video load times only in Teams so it clearly isn't just something on my end.
• It randomly loses the ability to connect. Everything else works including other MS products but Teams won't connect. Within the last 2 years, there have been at least half a dozen times where I turned on my computer in the morning and everything works except Teams. After a lot of searching for a solution, the fix was to delete two registry keys. Seriously, I have to go into the registry occasionally to delete two keys that are in no way tied to Teams based on their location in the registry before Teams will connect again when this happens. What the fuck is happening that Teams relies on two obscure registry keys that aren't even located under any MS Teams nodes. Fucking awful.
• Did I mention performance? It is worth mentioning again because of how terrible it is. It is usable and gets the job done but people have no idea how much faster this could be if the bloat was removed. Slack isn't exactly great from a performance perspective either but (at least in my experience) it's much better than Teams.
• I keep getting prompts about copilot in Teams which is infuriating considering I've declined every time and it's still enabled and still prompts me. I don't need AI to summarize a one-sentence chat message FFS and I certainly don't need help writing that sentence. Stop interrupting my flow to popup messages about features I've already told you I don't want to use.

The majority of the above comes down to bad design leading to bad UX and performance. Why are they using a Streams instead of rendering the video in-app natively? Because it was cheaper to just tie into their Streams service. Why is it that only Teams randomly loses the ability to function? Because for some reason it relies on a legacy registry connection key because...reasons?

There isn't a single bad thing about MS Teams, it's a bunch of kinda bad things that together make the product terrible. We should demand better of our software products but all leverage has been given to the people who already control these things so we're just screwed from getting actual good software made.

you must be in management, because all that was bullshit.

Well if you compare it with shit you set the bar unnececarily low.

If you actually can and want to look for something better that feels teams-like enough and actually doesnt suck?

Give Mattermost a shot. Its FOSS and comes with a Paid Option - for Corps of a Size where you want active support.

Comp I work for uses it and I fucking love it.

My biggest problem with Teams is that it doesn't deliver messages when it thinks the computer isn't active. Got Teams running on Computer A while you're working on Computer B? Don't expect to see anything from anyone, not even if you frequently glance over at your other monitor.

I got a mouse wiggler just so that I could get messages.

The most fundamental feature of a messaging platform is messaging. If it can't do that properly, which for some reason Teams can't or won't, then it deserves all the hate it gets.

Because it's buggy trash software with a terrible UI

Had you said Teams is the most comprehensive collaboration platform I would have been right there with you.

But Teams is really just a Sharepoint front-end with tacked on voice and text chat. It’s not a messaging platform.