The uncertainty is caused by the UK not having a plan or putting forward proposals grounded in reality. To be honest the only thing Brexiteers have had in common was that they believed in the idea that the UK should leave the EU. Problem is that everyone seems to have their own idea of what "leaving" would be so there's no coherent plan.
How is this the result of their own actions? From what I can tell Remainers have accepted that Brexit is going to happen, the question is how badly will the government cock it up.
The UK is going to leave, they've already put in their paperwork to do so. But that's not the cause of the uncertainty, regardless of you wanting it to be.
Besides, you're allowed to oppose policies outright, that's the point of a democratic society.
The other problem is that the official position of the EU is that the negotiations should not be successful. That the UK must suffer for leaving the EU. The EU is philosophically opposed to a win-win solution. The preferred EU option is an EU win - UK lose outcome.
The EU negotiating position is by definition illogical; there must be no barrier between the UK and the EU (at the Irish / UK land border); there cannot be a barrier free border between the UK and the EU. The only logical solution for the EU is a barrier free border between the UK and the EU but they cannot agree to this because it would mean the UK would not suffer from leaving the EU and the UK must be made to suffer for leaving the EU.
Without a fundamental change in the EU negotiating position I cannot see an agreed solution.