Google Calendar can now let you know when most or all of your invitees can't make your meeting, so you can choose to cancel or reschedule the meeting and reclaim your time. You don't even have to go into the event's details or keep track of responses in your email - an alert appears alongside the event. 

Organizers can click on the meeting to take one of the following actions:

• Delete the event - all other invitees can remove it from their own calendars
• Reschedule the event - either manually or with "Find a Time"

Guests can block the flagged indicator for the meeting until a new time has been set.

Learn more at https://gsuiteupdates.googleblog.com/2018/06/know-when-everyone-has-declined-google.html.