Indeed Starmer never mentions the B-word. But he should because "B....isn't working". We do need a more sensible relationship, our trade is being destroyed along with our tax base.
No tax base and we can waive goodbye to functioning public services and all the nice things like decent health and social care
I don't see there is any point Starmer saying any more than he has. Every time he mentions it Johnson would say "if Captain Hindsight had been in charge we'd have had no vaccine rollout because he would have followed the dithering EU". This is a gross exaggeration but it has sufficient an element of truth to it to make it a plausible criticism of Starmer.
At present labour need to do whatever is needed to make it more likely they will win the next GE. A lot of that involves saying little. Till the election. Resurrecting old battles that Corbyn lost, like Brexit, would be ludicrous.