@Pent: De-alignment between GB and NI might have been do-able if not for the DUP and Tory right wing, that's true. I think the ERG would've blocked it even if the DUP hadn't, though, so it would have required something much more cross-party, and that's been a basic problem throughout in terms of producing a deal that people could accept.
@Clockwork: Agreed on this showing huge systemic issues. One of the reasons the EU is so baffled by this is that most EU countries have systems that are much more multi-party and consensus driven and used to hammering out deals across the internal political class: the fact in the UK that Labour and the Tories have very, very similar Brexit policies but simply won't agree between themselves for political reasons is bizarre to, for example, Austrians for whom a Socialist-Conservative government is their usual style of governing coalition.
As to what happens if we just crash out - I agree it's unclear, but "a mess in which we come off a lot worse than the EU" seems a pretty good general starting bet. They're better prepared for it and less exposed to the results than the UK is. Like, I think a world in which the UK had super effectively carefully prepared for No Deal and could use that as leverage maaaaay exist in an alternate timeline, but for better or worse that's not the one we're living in. We literally had our government nearly give an emergency No Deal shipping contract to
a company with no boats. You go to Brexit negotiations with the government you have, alas, not the one you'd like to have.