Everyone maintains regular office hours: set times each week during which they’re always available via video conference, chat, and phone. During these times you can digitally stop by and chat without a prior appointment. (For more on office hours, see this excerpt from A World Without Email on the topic.)
If you have a topic you want to discuss with a group of your colleagues, instead of gathering them all together in a new meeting, you instead visit each of their office hours one-by-one to talk it through.
In many cases, these one-on-one conversations should be sufficient for you to reach a resolution on the issue, or at the very least, reduce it down to a very targeted set of questions that can be much more efficiently addressed.
There are so many things that we can and need to do in order to reduce the overwhelming number of meetings many of us participate in. This is a fantastic option.