A less cynical generalisation:
"Remain or leave didn't come close to giving people any sort of control over the actual fate of the country after this extremely risky move"
and
"Maybe people should be able to say whether they like the final terms as well."
But what the Remain camp want is to stack a referendum such that the choice is "Do we leave on these terms?" vs "Remain". But a much more realistic second referendum is "Leave on these terms" vs "Reject them", or a three way battle between "Deal", "No Deal", and "Remain".
I think a referendum on the final terms is nuts, from a pro-Remain perspective, because it dramatically increases the likelihood of a "no deal", cliff-edge Brexit (unless you mange to construct the question, and get it through parliament, in such a way that it closes off that possibility. And if you are happy for parliament to make decisions about which options are presented to the public why bother with a referendum at all).
All of this is besides the point anyway, because there is no window for a second referendum before we leave. We are legally leaving. That ship has sailed.
The tactic now has to be: extremely long transition, reverse the decision in a GE manifesto (by either promising to reenter the EU from the transition state, or promising a referendum on re-entering).
There's not really any course to plot though - either we remain within the single market, thereby rendering Brexit mostly a pointless waste of time, or we leave the single market, enact a hard border with Ireland and violate the GFA in the process. As it stands May and Corbyn both support the latter option. In spite of its obvious danger. Remainers have every right to call them out for that.
But a referendum isn't a solution to that is it? You are just articulating that the public voted for a stupid, incoherent, undeliverable course of action. I don't see how the solution to that is to ask people to vote again on a similar but slightly different question. As I said to
@Ubik the only politically viable question would have to permit a 'No Deal' answer, and if you want a referendum constructed in a way that denies them that choice, why even bother.