u/ProfessionalPear9028

Learn the map, claymore, mines, angry turrets, lurker spawn points and objectives, important defenses that needs to be priorotized, learn choke points (very important when all of your teammates are down. Ex: in top of the train in New York 1).
Upgrades your guns, set your class perks (I preferably set my perks to support the whole team instead of my own)
Learn your role (Ex: as gunslinger your job isn't to get the most kills, its consistent damage and neutralize special zekes quickly, I personally just get all the damage increase on special zeke perks).
Headshots, I can not stress enough the importance of headshots in extinct, if you can do it consistantly in chokepoints zeke will never even touch you.
Also if you are not Slasher or Vanguard use your melee wisely. As a Gunslinger I NEVER use melee to kill, I only use it as a tool to keep distant, 1 melee --> shoot --> 1 melee. Wasting a melee attack is detrimental if you are cornered, keep calm and have a strategy to get out.
I feel like this should be bare minimum unless you are godlike at the game but please please please have your class maxed out, preferably with all the prestige perks, I have seen way too many people with level 15 on their class running into zeke and just dies.
Play around your perks, and learn perks combos, as Gunslinger that always takes Front Line Supply perk, headshots to me are very important, if I could manage to get the Multi Barrel Shotgun I can delete Juggernaut without wasting a bullet in under 3 seconds, this perk combine with the one that gives equipment charge when headshots when combined allows me to save supply bags for other roles. Or if I am playing Slasher I will take the Tomahawk melee weapon combine with the consecutive melee kills gives bonus health, that's twice the bonus health.
Other small interactions that no less important like letting the medic revive because they can heal after doing it, or just take as much as explosive ammo when you can because the Fixer benefits from it.

8.1 Or pinging every specials right when you see it so the team can know or look around you when your character say something like "I see a big one" or "careful, lurker near by".

8.2 Or better yet, DO NOT FUCKING STRAFE DURING A HOARD, pick a spot, either crouch or stand up and stay that way unless you absolutely have to move because teammates behind you can't read minds, friendly fire HURTS in Extinction.

8.3 Or things like paying attention to all directions and stay that way during a defense is also important, look around you and see what possible direction zeke could flank that no one is watching and fill it in and learn specials's weakness (duh)

8.4 Directional melee, I use melee to cancel the reload animation and when you press "S" and "F" the character melee behind you without changing your view, I use it to clear of any zeke behind me and to avoid falling down an edge in front of me.

I think that pretty sums up how to git gud.

P/s: get the red TV charm, it will light up and give static sound if there are lurker or loot near by, if you hear static sound, slow down because 100% you need to pay attention.

P/s 2: I am not a god like player, I may not covered everything, in fact I dont know choke points for half of the maps.

P/s 3: Please don't ruin other's Extinction game because you want to magically carried through a level, learn the game, mechanics before dive in, call me a try hard if you want, its Extinction, it is suppose to require trying hard

At long last I have finally achieved it

Saw a newbie asking how to improve gameplay in Extinct/ Insane so I figured why not post my tips for others