They are worse than stagnant. They just took away what I (and a lot of my coworkers) feel was an important feature -- the ability to leave a thread open as you change to a different channel or DM.
From my perspective stagnant would be better than taking away useful features.
Teams chat has long had an obvious and fundamental feature -- ability to open a thread or conversation in a new window. And have as many of those open as you need.
Slack, by design, makes it painful to engage in more than one conversation at a time. It's so annoying to maintain a "save for later" list of things you need to come back to, or mark things as unread.
You can do this with slack by using the web client, but that has its own annoyances with not being a native application.
If the Slack desktop app had a way to open a workspace in a new window I'd put the Slack window of each of my customers in the virtual desktop of that customer instead of having to move Slack to the workspace of the moment.
Except for that, they could stagnate. For example, what the huddles were for? Did I miss any new functionality that they added to the old calls?
The customer of mine that pays for Slack uses huddles. I never thought about entering one that I was not explicitly invited to. I hope it's possible to make them private.
All the customers that are not paying for Slack are using Meet. One attempted to use Teams once but it's too complicated. Zoom for work calls? It surely happened but I can't remember when. Skype, I had a customer using it and actually screen sharing in Skype is good: it wastes as much of the screen in useless borders and toolbars as all its competitors but at least it's possible to zoom and get a pixel perfect view of what is shared.
From my perspective stagnant would be better than taking away useful features.