Yammer was acquired by Microsoft in 2012 for US$1.2 billion and I think they had great expectations of it becoming a corporate social network. Equivalent to Facebook for companies.
But I doubt that this has realized for them. Yammer’s integration with Office 365 is confusing and flawed. For instance creating groups in Yammer has no correlation to Office 365 groups unless you specifically set it up that way. In this video Office Guru Darrell shows how to do this. But be very careful doing this, because once you’ve done this you can’t undo it (except by creating a Yammer ticket – and even that’s not straightforward).
Also you would think that once you’ve set this up, you should be able to join existing O365 groups. You’d be wrong! Enabling O365 connected groups allows you to create new O365 groups through Yammer which is then appropriately surfaced to SharePoint & Teams as well, but despite a popular UserVoice idea from 2018, you still can’t join existing O365 groups. For me and I suspect many others that’s a fundamental flaw.
I think there’s a lot of value in a fully integrated Yammer especially in light of the recent Facebook Workplace launch, but even after being part of Microsoft for 6+ years, Yammer just doesn’t have the maturity to realize the value. I also don’t see there being much momentum in terms of developing this product if one looks at the frequency of feature releases over the last 18 months.

That is juxtaposed to the fantastic value that Microsoft Teams provides. And I wonder if that is not the underlying issue. Teams is a runaway success for Microsoft – it is in fact their fastest growing app in Microsoft’s history, an incredible statistic! It is set to surpass Slack in short order.
I wonder if teams aren’t so enamored with the incredible integration, functionality and value of Teams, that Yammer’s use case isn’t immediately clear anymore and that for that reason it’s not being adopted anyway. Which means that Microsoft are hesitant to invest and develop this product. And as Teams continues to grow, I struggle to see a clear path forward for Yammer.