You're missing the point. The backstop means that the UK can't negotiate ANY trade deal with ANY other country. That is clearly unacceptable.
The EU have been told over and over again that keeping to the GFA does not necessitate the onerous backstop - but it doesn't suit their negotiating position to accept that, so they just keep saying, 'Non.'
The EU have been told over and over again that keeping to the GFA does not necessitate the onerous backstop - but it doesn't suit their negotiating position to accept that, so they just keep saying, 'Non.'