A lot of comparisons between Britain and France lack particular context which is that, Britain replaced its right wing to far-right party with a right wing party. France may well have defeated its far-right with a diverse left-of-centre coalition.
I understand the desire to grasp for something, but Starmer is not comparable to Melenchon (in fact if the left coalition gets to govern he will outright refuse to work with them)
This is more directed at Yanks going "oh look at Britain and France they defeated their right wing parties" when at most France has done that and we've ushered in a group of people who actually sit to the Tory Party's right on half of the issues.