Adding a bit to that, the EU made clear what its terms, dictated by internal rules and treaties (for instance, the Good Friday Agreement forbidding border controls within Ireland) would be and those terms haven't changed.
The UK has multiple times tried to ask for terms that violated previous agreements and that was refused.
The pain for the UK is entirely self-inflicted. It was clear from the start it was a foolish idea. It's clear now it was a foolish idea and it'll continue to be abundantly clear it was a mindboggingly foolish idea from the start.
This is a very pro EU biased view. To assert the EU governing body is not playing politics in brexit is absurdly applying a historical vacuum, ignoring the history of how tensions have grown and based on a modern narrative posthumously.
The EU decided to force the currency issue with their largest economic contributor, and imo chose to die on that hill. The EU has threatened to hold Britain 'accountant able' by being intentionally obtuse and treating to impose artificial barriers for new agreements.
_How_, though? It's hard to see how much more accommodating the EU could have been without fundamentally compromising itself.