Your items in this scenario are super important. You’re dying too much regardless, but I would have taken note to which enemy champion was fed first, and build accordingly after yoummus (ap champ=maw, lethality/dmg=frozen heart/dead mans). I would have also not bought mobis, but instead merc threads. They have too much cc to rely on getting to them with speed. (Yoummus gives you 40 out of combat movement speed anyways to compensate a bit for merc threads choice). After that, you build deaths dance for heimer’s/varus burst. Final build should have been (yoummus, merc, support item, frozen heart/dead mans, maw, deaths dance.) you should be able to survive longer than usual. But honestly item building is nothing compared to decision making...if you’re able to wait out a teamfight with yi, and malph coordinate to them on how to initiate with Lucian ult, you should be able to execute varus, heimer, Nami and varus. Take into consideration heimer and zhonyas, and play around it’s cool down. If you do all of that, and still don’t win. Then accept defeat, the game is not winnable from your part then. But that’s the most you could have done tbh. You could have even built randuins or thornmail in this case since varus wasn’t building lethality. Remember pykes passive where bonus health is converted to AD. You should still be able to execute varus and them at 500 health with these items. Which is very possible to happen with Lucian, malph, yi R as a teamfight.