The reason the EU always wanted to have the UK on board had more to do with marketing than with necessity: Europe is France, England and Germany; if the EU was to be Europe, it needed those three in it or it isn't going to happen. It's also Spain and Portugal, Belgium and the Netherlands. The more the merrier. Open a history book and if a country playing a major role on the European continent is in it, it should probably be on that list.
But the EU now already exists and the UK has been so insistent on having a special status that Europeans have gotten used to the idea of the UK not "really" being in it despite being just another European country like the rest of us.
It's okay.
You can leave.
We no longer need you for the EU to be able to exist.
We tried to accommodate you and make it work but we've understood that the feelings aren't mutual.
We'll still keep in touch with your extended family, though, and maybe over the next two years we can find a way that you can still come over to party sometimes, or y'know, just hang out if you feel like it.
No hard feelings.
Don't be a stranger.