I think I agree, UK was not the weakest song. It's a bit like the songs Germany submitted a couple of years ago (thinking of our 2016 song, for example): It's competent, harmless and average. Problem is, you need to make people vote for you, and you've got to stand out. There are only 10 teams you can give points to (12,10,9,8,7,6,5,4,3,2,1). You can have the 11th best song in Europe overall, but still end up with zero points, if you are exactly at 11th place in every country.
Germany's song was much worse, but I guess some judges liked to be slammed with that wokeness hammer and they gave us three pity points. Other worse songs were those spectacularly cheap, but effective songs like Effendi and Loco Loco (Serbia and Albania). They kind of stood out for their open shamelessness, and I kind of liked that.
Also, it helps to have some allies, I guess, really strong allies, like Greece and Cyprus. Or Moldova and Bulgaria. But that only takes you above zero, hardly above 100 points.