I think the problem is that Brexit was never about becoming ‘self-reliant’. As you said, Brexit cut the UK off from their single biggest export market, which is the exact opposite of what you need to do if you want to build up your industry. These days no country is completely self-reliant, and trying to be so, while it sounds good, just ends up meaning that you generalise, becoming mediocre at everything and exceptional at nothing.
If the Brexiteers truly wanted to make Britain great again they should have chosen a domain to be great in and lobbied for investment in it. Britain was already punching well above its weight in financial services, they could have invested further in that, for example, and become a true world leader… but only from within the single market, where they had unrestricted access to the talent and economies of the EU.
Yeah, globalisation has caused lots of problems, working class people have suffered even as the wealthy have flourished. But there’s no going back. A small nation like Britain couldn’t be completely self-sufficient without essentially regressing to a lower technology level, at which point they would just get invaded by somebody with an advanced military.
Instead we need to look at other ways of righting those wrongs, new strategies to ensure that the people can live happy and healthy lives. Lots of people want UBI, and I can see the attraction. I think it’s worth a try, even if it doesn’t work as advertised we could get feedback and adjust things until we find something that does work. The status quo is just not tenable.