The UK has long had a dire need for constitutional reform–especially, some entrenched protections against the built-in possibility that any sufficiently large English majority can lord it over the other three constituent countries. Maybe they should have addressed that far more fundamental issue first, before holding a referendum on EU membership?

The failure to do so has likely hastened the UK's own demise – the experience of being outvoted on the Brexit gave a big boost to pro-independence sentiment in Scotland, and created a pragmatic case for Irish reunification which did not exist before (and stands a chance of eventually winning over even many who are culturally predisposed to oppose the idea.) While I think both outcomes are still many years away (especially in the case of Northern Ireland), it seems likely they'll be with us much earlier than they would have in a timeline in which the Brexit referendum had gone differently.