How did it not work out? A lot of things the EU claimed were red lines ended up being crossed. Look at the Horizon programme. Supposedly an inviolable "privilege" tied to FoM, the UK called the EU's bluff, left, and UK is now back in Horizon anyway.
Perhaps with the fact that immigration hasn't stopped, the economy is a much bigger trash fire than any of EUs and the fact that people still don't seem to be happy and keep pushing even worse laws.