Bullets: Can’t dodge instant and why that is a (solvable) problem
You don’t dodge bullets. You can hide behind things, crouch, or leap around like an idiot to make shots harder for the opponent to line up and time, but once they pull the trigger you can’t get out of the way. In fact most games don’t bother to do all the physics on how much a bullet drops or calculate how long it would take to reach where it eventually hits and just treat a bullet as if it travels instantly towards its destination.
There are exceptions such as ARMA and Battlefield games, but choosing to not do this is typically perfectly fine because you aren’t aiming and firing over distances that would noticeably effect bullets (such as a from one end of a room to another) and so not doing this is not so much a failure as it is a smart optimization.
You don’t dodge bullets but you can effect your chances of getting hit by bullets by playing smart and not standing around motionless in an open field. But even if you are playing optimally (hiding behind cover when you can, moving evasively when exposed…) these only lower your chances of taking damage they don’t mean you won’t take damage. If you are playing a game like Shovel Knight and take damage it is because you screwed up, enemies telegraph their attacks and you should be able to dodge them. In shooters though there is always the chance of getting hit even when you are doing everything right, which creates a problem.
Basically damage is a game punishing you for dong something wrong, and your health is how many mistakes the game will let you make before penalizing you. The problem in shooters is that you will take damage in shooters regardless of how much you deserve it because deserve has nothing to do with it, probably does. This puts players are in the unfortunate situation where the game may be penalizing players when they didn’t deserve it (by which I mean they are playing well).
It is kinda a background radiation of damage, players are constantly taking a bit of damage here and there and you can’t really fault them for taking those hits in the same way you would in Shovel Knight because they aren’t screwing up like they would be in Shovel Knight, they just aren’t able to dodge bullets.
How do games deal with this problem? Well, there are two basic models we can look at to understand how games deal with problem: Halo and Quake.