When dialed into a meeting, users can press *6 to mute/unmute. Please see https://docs.microsoft.com/en-us/MicrosoftTeams/audio-conferencing-common-questions#what-in-meeting-dial-pad-commands-are-supported for further information.
I thought this was Skype parity, but stand corrected… my apologies. I will investigate presenter ability to unmute attendees with the feature team. Thanks all.
The team is looking into this feature and considering solutions. We will update when there is more information to share.