No, not that. Before you accept this received wisdom, consider what status any promise or plan made by a cross party...........cross-party............campaigning group would have had with the government post the referendum. The answer, of course, is that it would have had none at all. I don't know why I have to keep saying this, but why would a Conservative government feel in any way bound by a promise or a plan made by someone opposing the official government position, whether it from their own party or the opposition? Why would Cameron or Osborne (Conservative) have taken the blindest bit of notice of a commitment made by, say, Gisela Stuart (Labour)? Offering such an unfulfillable plan or promise would have become the single biggest piece of dishonesty in the campaign, and, further, would have been akin to Leave handing Remain a huge stick to beat them with.
For people to keep on repeating this crap about lack of a plan, (it's become some sort of mantra for the Remainers), is indicative of nothing other than a lack of thought on the matter.