I don't think the idea of a vote on a deep constitutional matter is wrong. But I think it only really works when you have a government saying "we propose to do

I don't think the idea of a vote on a deep constitutional matter is wrong. But I think it only really works when you have a government saying "we propose to do X, but we'll only do it if the people consent in a referendum". What doesn't work at all is having a referendum offering a major change that the government proposing the referendum thinks is a bad idea.