I agree, it's bad. We were on Slack before, but switched to teams when going all in on Office 365. I really wanted to use the "Teams" feature in teams, along with chat for general chats not specific to projects. That never panned out.
We'd never see communications, even with notifications, in the "Teams" area of teams. When I did think to look at the conversations, all of the additional whitespace and padding the Mac client adds (not sure if it's all clients) on the messages in the "Teams" area just made it very difficult to consume context around a single discussion. There were another annoyances, but we didn't use it long enough for me to remember what they were.
We now just use the "Chat" portion of teams for all conversations and rename multi-person conversations with the project name. Starting a new chat with the same group of people for a different project is far more difficult than it needs to be, but I understand that's probably not the use case with how we're using it.
Search is abysmal. When clicking a result, you jump to the message but it is invariably devoid of any contextual information. It's just the message, by itself, in the chat window. It's only use is finding the date/time for the message you need, then scrolling back (for minutes sometimes) until you find the conversation from 3 weeks ago. And then, all the reverse infinite-scroll loading makes the client slow down to a crawl.
We routinely have issues with images not displaying. Sometimes loading the larger version works, many times it does not.
We routinely have issues with messages going completely missing in 1:1 chats. The sender can screenshot and show the message was sent, but the recipient never receives it, even after restarting the client.
I often get notifications of a new message in a 1:1 chat and when I goto the chat, I'm at the end of the channel and the message isn't there. I have to scroll up and then scroll back down so the infinite-scroll will load the missing message.
When in the new message box, I can CMD + UPARROW to edit my last message. This is useful because I make a lot of typos and fix them after sending/reading. A bad habit, perhaps, but it's how my process works. Anyway, this doesn't work if I someone has sent a message after mine. Teams is not smart enough to let me edit my last message with CMD + UP unless it was the last one sent. I have to switch to the mouse to make the edit. Also, if I CMD + UP in time to make an edit, submit it, then realized I missed another typo (it happens), CMD + UP no longer works. I have to manually focus the "Type a new message" box again and then it'll work. At that point I've touched my mouse, so I usually just opt to right click + edit the last message.
Sometimes after waking up my Mac, the teams window is missing. This happens to outlook too. CMD + TAB to focus the app doesn't retrieve it. I usually have to "launch" teams or outlook again (while it's still technically open) to get the window to reappear. No other App on my Mac does this, just Teams and Outlook.
Given how we use Teams, I like to "pin" chats for specific projects. I'm limited to how many I can pin. Why?
This one is minor: Gifs loaded with giphy can be paused. Copy/pasted gifs cannot. They auto play forever, which is annoying when it's the team chat I keep focused 90% of the day, but the conversation is slow that day.
I'm sure there are other things I'm missing.