Whether the last three years were wasted time or not, they were also packed with negotiations. It's therefore naive and frankly insulting to say that the EU refuses to negotiate. They already did, they can say, and perfectly correctly.
On the other hand, they've now negotiated a deal and it has been rejected and they've been told that they have to back down. But all their members are in agreement with the terms of the deal, from their end. The WA has been signed off by the EU Council. Ireland wants the Backstop, and it would be a betrayal of the Irish to buckle on that front.
It seems that the position of the UK now has become one of -- how can I put it? -- trying to pretend that we are bigger than the EU? Or at least the same size. But both of those presumptions are wildly false. It's the origin of the "they need us more than we need them" lie. The EU is ten times our size on nearly every meaningful measure. So how can it ever have been true that we could expect the EU to come to heel, to listen to and to accept our demands?
cassa suggested earlier that "the UK can't have [red lines] it seems". That's not actually true. It's just that red lines also need to be grounded in reality and pragmatism. Right now, the leadership of the UK seems to have lost that. It worries me that people are welcoming, or even celebrating, this.