Well, if the prodigal son returns to the fold, and rejoin, he will be welcomed, but things change, and it is very likely some changes in the EU will not agree with British sensibilities. And you will have to pass through the adhesion process for first time, which you may not like much.
We have always knew the UK has its issues, as everyone else does, and some of them are very, let's say, whimsical; Brexit was a surprise, but, for better or worse, the British never were boring. We are very used to it.
Of course, the UK doesn't need to fully rejoin, as many other countries never have done. Your choice.
In fact, in many ways, you never left. There is no way to understand the UK without Europe or Europe without the UK. Too much history and geography.
My first reaction to Brexit was 'Fuck them, who needs them? Let them go and never come back! They were a pain in the ass anyway'.
But watching British politics from the outside made feel pity for them. And when I compare British politicians with French, Spanish, German or Italian, I find so many parallelisms that the UK starts looking like an alternate world version of any of them.
Are the British a bunch of morons? You can bet.
Has any country in the EU a shortage of morons? Far from it.
That makes you see things differently.
Should we wait until Farage and his ilk throw themselves into a pit to welcome the British back? I'd say yes, but how much of the UK will be there by then?