It is standard negotiating OP by both sides. Just take a look at the Troika / Greece negotiations: breakthroughs come at the very last minute.
Extending the transition period merely lengthens the phoney negotiations.
> There is no exit that puts the UK in a better position because it imagines itself to have power and influence that it does not possess.
Viewed through an economic lens, Brexit will do damadge, certainly in the short term. Medium to long term depends on whether the Tories learn drop austerity and to love Keynes . It seems Sunak does, going by short record so far.
Viewed through a political / sovereignty lens the argument for Brexit is on a stronger footing.