There were no real negotiations, and there were never going to be. This has always been painfully obvious to anyone with even the slightest interest in EU foreign relations. The options on the table have always been the same:

You can be like Norway and join the EEA: full access to the single market, but having to make a financial contribution, accepting most EU laws, and with free movement of people. You get an exemption on some laws, but you don't get a say in any of the rules of the single market.

You can be like Switzerland and join the EFTA: partial access to the single market (notably not the banking sector), still have to contribute, only have to follow EU laws when it comes to trade, and still free movement of people.

You can be like Turkey: a customs union meaning no tariffs apply to EU trade, but you have to apply EU tariffs on all other trades and have no say over them.

You can be like Canada: a comprehensive free-trade deal which covers the majority of goods, but it means having to follow EU standards and requirements without having a say in them, and it probably won't cover services.

The EU was never going to give every Briton a magical gold-shitting unicorn, no matter how much the UK was going to plead and beg for it. It was more than happy to negotiate a deal on any of the options like those above, but it was up to the UK to decide what Brexit was going to look like.

But the Brexiteers promised the voters they could have their cake and eat it - "Brexit means Brexit", after all. Everyone invented their own personal idea of a Brexit, and the various interpretations were always going to be fundamentally incompatibly with each other! The negotiations went so horrible because the UK had absolutely no idea what it wanted, and any option was going to be wildly unpopular as it did both too much and too little at once. And all of that is before you take Northern Ireland into consideration, where the wrong move would result in a literal civil war...

Brexit wasn't a negotiation. It was a therapy session to help the UK find itself.