Err...the country was being led by the same guy people now hail as one of the country's greatest heroes, the same guy who eventually beat Attlee again six years later, albeit on the technicality of the electoral system. Granted, Churchill's post-war campaign misjudged the mood of the country terribly, but he certainly wasn't the weakest opposition a government had come up against.
Personality-wise I'd argue Attlee and Boris are/were vastly different. Attlee was never really a showman, instead someone who viewed himself as the head of a collective cabinet with a lot of competing views, a strong managerial figure as opposed to the country's esteemed and absolute leader. Boris, meanwhile, is someone incredibly obsessed with himself, a self-styled larger-than-life personality who desires the attention to be placed on him specifically. The Boris-Churchill comparisons make sense on a surface level; Boris-Attlee doesn't place except for the fact that both men will presumably be looked back on as men who held the office of PM.