Shot Aiming in 2k21

I recommend watching videos on shot aiming tips, to be able to figure that out!

SOH Pro

Don't run around corners

Practice and aim low

Cod is a fast paced game so you have to adjust from other games like Halo, which are somewhat slower paced. I recommend using sleight of hand because that's what will give you faster aim down sights and might guarantee winning the gunfight, but not always.
Even if you get the first shot on a guy, he might still kill you due to the bad hit detection in this game. I've learned to deal with it though so it's no biggie for me.

What I suggest you do is play Team Deathmatch where the pace is slow(most of the time) and then when you feel you're up for the challenge, play some objective game modes like Demolition or Headquarters. They can get pretty hectic at times.

Oh and one more thing, you might be using bad guns. I recommend trying the Famas and Ak-74u for now. As you level up, try to get a feel of other guns and see which ones you like the best. I use nearly every gun with the exception of Lmg's because they're
just not for me. Hope this helps and if you need any more help, feel free to ask.

sLEIGHT OF hAND pRO aims down the sights faster. I cant help you with LAG though, its very minute sometimes, but its a part of online gaming. Steady Aim helps with hipfire accuracy. Also checking your controller "sensitivity" may help. Check that through
in game options. Lower means turning slower, but better for aiming down range.

The case of "steadier aiming" is just luck.

Many times you will notice that sometimes your weapon just has ridiculous recoil and other times it's incredibly stable.