Why should a prime minister need to seek a consensus to leave the EU
Because, as you know, there are four possible options for future trade with our largest trading market, the EU, and possible shades of variation beyond that. The referendum did not specify which option voters or the UK wanted, and Theresa did not know when she sent the resignation letter.
Our idiot Brexit Secretary, David Davies, wasn't even aware of the options and what was possible and what was impossible.
Theresa forced our highly experienced UK ambassador to the EU out of his job, and refused to listen to anyone with knowledge or experience. Hence she ended up with an unworkable "agreement" that Parliament rejected.
That's why we would have done better with a competent Prime Minister who agreed the UK's objectives and plan before sending the resignation letter.
I don't know if you've ever entered negotiations without knowing what you wanted or what you could afford to pay, and if you'd sent a letter cancelling your previous contract before starting negotiations for your new one. If you have, you're the same kind of idiot as Theresa.