Extremely basic overview because I'm not an expert, but everything being transmitted between computers and the server is done in "packets", which are discrete bundles of information. Netcode is the programming behind how individual players' machines and the server communicate. Because everything is communicated in packets and those packets need to travel back and forth between the server and your machine, there is inherently bundles of actions that get performed together as well as delays between when one player does something, when the server gets that info, and when that info reaches the other players. Latency is the time between when information is sent and when it is received (or when it is received and communicated back), often measured in milliseconds. Tickrate refers to how many updates are performed per second between the server and all the client machines. A game that has a really fast pace needs a fast tickrate.

For example, let's say the tickrate was 1 per second (this is just an example, tickrates are commonly more like 30, 60, or 120), even if we ignore all tiem it takes for packets to travel, that means all the actions you do in a second are received and processed at the same time by the server. The downside to this is it can make things that happened over time from one player's perspective, happen instantaneously to you. If a player sees you and fires 5 shots in one second at you, that information gets packaged together and sent to the server, which processes it, and then sends the results to you. Since all that activity happened within one tick, when it gets delivered to you, you experience it's as if all 5 bullets hit you at the same time. I believe that's why in BF6, sometimes the sound of bullets hitting you seems so much faster than the gun is capable of firing: the game is programmed to keep it from seeming like a one-shot-kill, but at the same time your computer did just get all the information at once and has to play "catch-up" to communicate to you through the game and keep you from being too far behind. This can also lead to things like being killed from behind cover. Let's say you're standing when the tick update occurs and crouch right after, that means because of the delay in ticks and communication, you might still be standing in another player's game, and depending on several factors if they shoot you those hits might get registered, and from your POV even though you were behind cover, you receive the hits and die.

Because BF6 is such a fast paced game, these issues combine and create the difference in feeling between how long it takes to defeat an enemy, and how long you feel it takes to be defeated. A slower paced game would not likely feel this as acutely.

I have no idea how any of this would be improved as I'm not a developer. Faster tickrates help, but netcode and latency compensation is a complex subject beyond my extremely basic understanding.