The UK did look at the evidence to the level of scrutiny as agreed in the extradition treaty and decided he should be extradited. This isn't some hypothetical, Assange got a fair hearing at every court in the land up to the supreme court, and the judges came to the conclusion that he should be extradited. This isn't some hypothetical, it is a matter of law that his extradition is legal.

And just to put a real fine point on this: The UK judges all the way up to the Supreme court did look at the evidence, and decided against him. Which I would say is a much more reasonable approach than your argument that he shouldn't be extradited based on not having looked at the evidence for a while. It's not even like it's incomprehensible, they published their judgements at every single stage. Here, it's page 27 of this document: https://www.judiciary.uk/wp-content/uploads/2021/01/USA-v-As...