There are multiple ways in which people can participate: mailing lists, direct mail, onsite at a meeting, remote at a meeting, chat, github comments/PRs, submitting documents. Is there any reason not to cover all of these (and any I’ve forgotten)?
WG chairs are in charge of the lists or whatnot that their WGs use, and that seems to work OK. When it doesn't, it's more the chairs not using the tools they have than the tools being inadequate.