You do realize the fact that this is literally a major update for L4D2 after 10 years and first update in a long long time after Valve dropped support for the game? Us TF2 fans have only waited 3 years for now with still tiny little updates in between, unlike L4D2
‣ The Last Stand campaign
‣ The survivors decide to take an alternate path in hopes of salvation, but is this path truly safe?
‣ 30 brand new achievements
‣ New and unique milestones to strive for!
‣ 26 new survival maps
‣ How long can you survive against the endless hordes?
‣ 4 new scavenge maps
‣ 2 brand new melee weapons
‣ Hunt down a Jockey with the pitchfork or whack it with the shovel. Satisfaction guaranteed!
‣ The L4D1 infected are back, and they're bloodier than ever!
‣ New and previously unused voicelines for survivors - Rochelle has a personality now!
‣ New character animations - New, improved and overhauled animations by our skilled modding team!
‣ Reworked gun models and animations
‣ PvP enhancements and balance changes
‣ New attack spots, new tank spawns, and hundreds of new infected ladders for the competitive modes!
‣ Official implementation of CSS weapons
‣ The CSS weapons are now available to everyone!
‣ Brand new mutations Rocketdude and Tank run - Ever wanted to launch yourself around with a grenade launcher, or run away from hordes of tanks? We've got you covered.
‣ Improved UI options
‣ Every gamemode offers the singleplayer option, Versus Survival is officially brought to the main menu, easier gamemode switching, and new outro stats!
‣ Hundreds of bug and exploit fixes
‣ The days of falling through elevators are gone!
first update in 8 years, Valve is only officially rolling it out , the whole update is made by the community.
Something that Valve has done before with TF2 i.e having the community make update for a game and then launch it officially .