Aside from being a Tory/right-wing policy, the way that the Tories have approached Brexit, in terms of their 'red-lines' of no customs union or single market arrangement with the EU, made it undeliverable, and the most obvious indication of this is the NI situation which has been an issue from as soon as they tried to negotiate a withdrawal arrangement and is now becoming seriously scary.
Of course those proposing Brexit back in 2016, had they not been indulging in fantasy, should have understood this from the outset and addressed the specific NI issues, and they didn't: the changed approach to NI in Johnson's recent 'deal' shows that the Unionist part of the Tory-party name is now a joke, especially given the recent finding that the party would be prepared to lose NI and Scotland (and some of us Scots would happy with this) so that they got their precious Brexit. I'm struggling to see how anything other than revoking A50 makes any sense now, since I can't see how NI won't descend into chaos if any form of Brexit short of a customs union goes ahead, which won't happen due to Tory 'red-lines', and of course we will all be damaged by any form of Brexit.
Cancelling Brexit and immediately reviewing options for the either the break-up or radical reconfiguration of the UK would make more sense. The GF agreement provides for a border poll in NI, so that should be sanity-checked, as should the current consensus as regards remaining in the EU in each of the 4 nations. I'd guess Scotland and NI will, just as in 2016, prefer to remain in the EU, I'm not sure about the situation in Wales, so perhaps it is only in England that there is still a majority for leaving the EU (and for the Tory party) and that might suggest that England (and possibly Wales) secedes from the UK unless the experience of the last 3 and a bit years will result in a majority for 'remain' too.
It seems to me, given the current situation, that looking again at the UK might be just as valid as thrashing about trying to square the circle of the current chaotic approach to Brexit, since it seems likely that the UK is already broken in terms of the political affiliations of the 4 nations.