Former microsoftie, here.
From years of observation, it seems Microsoft tends to ignore products in industries that are in 1 of 2 states:
1. Stagnant growth
2. Low competition
Skype is in the former.
It's embedded deep in the culture to follow rather than lead. (Edit: I should add that it's not that Microsoft doesn't try to lead, its just that generally they aren't very good at it. They are much better as a second mover. Far more so it seems than other companies.)
Most of their great products were a response to a rapid rise of a competitor.
Windows after Apple's GUI. Word after Wordperfect. Excel after Lotus 1 2 3. IE after Netscape. Azure after AWS. C# & .NET after Java. SQL Server after Oracle.
Once the industry stops growing or there is no competition, the product is neglected or drifts listlessly unless another company causes the space to boom financially again or gain mindshare, in which case Microsoft might start moving again.
(The only place where Microsoft truly leads is in developer platforms, because they are a company of developers, so they get it better than the other products they offer.)
Don't get me wrong, I use Microsoft products almost exclusively.
I've just learned to be very depressed when Microsoft doesn't face an existential threat with the piece of software I use. The product will inevitably drift and likely even get worse over time, until another company can create an existential threat (like Chrome has done to an extent) and literally drag Microsoft kicking and screaming into putting serious thought into the product again.
It's just in their DNA, I guess...
But when they do finally get around to it, they usually do something cool. See VS Code, WSL, etc.
So we just need someone to make Skype-like products cool again, and ideally start making millions upon millions in the process, and then Skype will improve. :)