Sovereignty:the ability for the UK to make its own rules and standards as an independent nation
The UK always had that, and actually to a much greater degree than it could outside of the EU, because for almost half a century the UK was actually able to influence or even veto the rules of the continent with its own while maintaining its own freedom to make domestic rules apart from the common ones, while right now it has completely lost that ability and even after the end of the transition the UK will just have to live with the rules the other
countries are making around it without any influence or even a veto which you voted to destroy.
I was about to reply exactly the same thing, but you did so already..
Allow me to add that the whole discussion about the economical benefit of Brexit is something that even Brexiteers timidly have admitted is something fabricated 'post factum', and that the business case for it will not be there anytime soon, if ever. (JRM estimated it at what? 50 years? That's a nice way to shift any blame for the lack of success till he's well gone)
Brexit was essentially about Britain's self-created immigration chaos, fueled by the ludicrous decision of successive British governments NOT to be willing to limit the influx of EU workers from the eastern memberstates when they could do so after their accession, combined with the very relax immigration policies for immigrants from the ex-colonies.
It created a Britain where cheap labour forces are abundant (a dream for employers), but where wages are stagnant because of it (a nightmare for employees): this gave both Labour and the Tories happy and wealthy party sponsors and it allowed the government to offset the appalling low productivity of the British economy through its low production costs, thus avoiding the need to invest more tax money on better education, more training, and costly apprenticeships...
Low taxes for businesses and citizens: everybody loved it!
It worked all so well on paper and in the spreadsheets for so many years, but the visual results on the streets were bewildering!
It's why DC utimately tried to negotiate a permanent hard limit to EU migration and got some sort of an emergency brake mechanism in 2016, and why TM spent 6 months after the referendum and before her Lancaster House speech trying to seperate the 4 freedoms: both knew very well that the 3 other freedoms were a real pitty to lose and impossible to reproduce through any sort of a FTA with the EU or even any other country in the world. The EU however said 'no cherry picking' and only then did the whole idea of a Global Britain came to the foreground, even if TM herself never believed in it herself.
'Global Britain' is all about damage control: trying to replace as much as possible of all that will be lost.