Feel free to disagree but I think that's incorrect. In Silver and Bronze, the champions picked are important but nowhere near as important as how they are played. I would never call a Bronze game a done deal at champ select just because of the two teams' compositions.
And their comp isn't unsalvageable. Minus the Malph, the enemy team's main means of initiation is running. Thresh is a great disengager here because of The Box. Malphite can ult in but Thresh's counter-ult is going to completely stop Rammus and Voli from charging in to join him. Both of them are also easy Flay targets because they're going to run straight forward to engage. With 4 of you defending a tower (easy wave clear with Sivir/Lux), Trinity Force Eve can split push and knock down towers pretty quick. With a vision advantage (no Sightstone on the enemy support) she'd be able to do so pretty safely.
It wouldn't have been a breeze, but it was winnable. Thresh could've helped the team more with less selfish itemization. Banshee's Veil and Sunfire Cape don't do that much to help the whole team. Where's the Frozen Heart to counter their double ADCs? Where's the HotM, Locket, Zeke's, Randuin's? Even with these items, you still might have lost. But not having them suggests that you didn't think they would help, which kind of shows one reason that you might be struggling to escape Bronze.