In the case of Canada, you're talking about a parliamentary decision, followed by a referendum, so it becomes a two-stage process. I certainly would not consider a referendum illegitimate in itself and I think a case can be made that a change in the electoral system is indeed a very important decision. I think the problem with referendums is that other issues often come to the fore. In Australia, for instance, referendums generally tend to fail because they just mean that the people can express dissatisfaction in general without reference to the specific issue of the referendum. I think, actually, that happened in the case of Brexit, too; that people did not always realize they were talking about this specific issue, but expressed general dissatisfaction.
On August 22nd, 2016. See this statement in context.