I had the same issue with ~30 fps in lobbies and 5-10 fps when fighting with render hacks showing 14 other people near me. I installed Optifine, Frames+, and BetterFPS and it helped a bit.
The real kicker is changing your render settings to highlight less people. Either disable things you don't need (like potions or strength indicators under nametags) or turn down your render settings. Vape v3 make this super easy for you, giving you a block range for people to start showing up.
Also, I'm assuming you already did this, but increasing your ram allocation in Minecraft using the JVM arguments helps a ton too.