Teams is too complicated to use for most of those people not specialists with computer, looks like it is much suitable for IT department. you know why Chinese WeChat is so popular? Just because its easy to start for everyone, even those who don't know how to type or how to use apps.
We don't expect everyone in the company knows everything about computer, but knows his work to handle.
To simplify the app, leave personal chat and channel chat together, people will know what they've missed. Do not try to group them by different tabs, leave this decision to users in the settings (well, you don't provide setting in Windows and Mac apps).
Or, do we must keep both skype and teams?
too many channels too many teams! That confused people to start communicating with colleagues. They don't know how to start, how to check messages, how to reply. So, why not make it as simple as Skype, just allow skype to send files, and store history in outlook!