Hello, rational British resident here.
The thing is: five years of this process has worked to make me much more pissed off than I was. It might not have been clear from outside just how toxic this all was, and will have driven many of us away from our initial position of "this was merely a bad decision that we will work around".
It’s not specifically about the mechanics of the EU membership or "leaving a historically recent trade union". There are rational arguments to support doing these things, and there are ways to do them while not being dicks about it. But the UK's internal political environment has crumbled along with this process. It's become bound up in a "culture war", and many of us reasonably feel that this is just one of the manifestations of a country which is taking a negative and inward-looking approach to situations where we'd much rather take a positive and internationalist one.
It’s hard to maintain a dispassionate attitude sometimes when being deliberately provoked. So you’ll see people using the words “evil” and “racist” not to describe Brexit itself, but rather to some of the people it’s inseparable from. Although the campaign itself was explicitly racist, featuring cliché lies about an incoming horde of foreigners. Really grubby stuff that should shame the country, and it's getting worse.
I've spent the past five years watching a succession of (primarily government) politicians lying to my fucking face about the great opportunities that await us. Repeatedly compounding a bad decision with completely unjustified rhetoric about it.
What we could have seen was a sensible approach that appreciated that Brexit was a democratically-made decision and had to be respected, and then tried to build a national consensus about how best to deliver it. But we instead went for a take-no-prisoners approach and this has left many of us quite angry.
Even just from a purely practical level, I'm pretty pissed about this. After years of nonsense the final outcome is that it's going to be much more of a pain in the arse to do a bunch of stuff I did that was easy before. I've lost a set of rights that I had, used, and valued, and gained nothing in return. I could even deal with that a bit better if I didn't have to be constantly lied to about how great it is.
So yes. The country won't be destroyed – but it will be permanently weakened, and I think it's okay to be a bit emotionally invested in that.