Consider this, Tits.
Let's look at two things as they relate to "performance" and how they influence gameplay and immersion.
1.
Dead tanks that disappear a given period of time:
First off, what world do we live in where 40 ton hunks of metal simply disappear after 30 seconds? (Probably the same world where a magnetic anti-tank grenade doesn't actually need to be placed on the tank to destroy it.

)
Now put that in the context of the game. Your team has fought well and knocked out an enemy tank in a particularly important area of the map. This dead tank provides great cover for your MG'er and now he can lay down fire for your squad as they approach the final objective. Your entire squad is now taking cover behind the dead tank and preparing to make their last assault. Then it just disappears and your whole squad gets wasted by 1 guy with a pistol. Yeah, that happens every day in a real war.
2.
Moving mouths and facial expressions:
Several years ago we all watched trailers for this game and were shown over and over again that the characters have actual facial movements that add greatly to the immersion and overall realistic feel of the game. Realistic touches such as this influence customers decisions as to whether or not to buy the game. So when a customer notices from the get-go that these features don't actually exist (because there is no disclaimer in the trailer that says the features are not actually in-game) they may feel like they have been deceived or worse, lied to. You know, because these extra animations "hurt performance". If these features "hurt performance" and weren't going to be included in the final product why in h&ll were they even shown in the first place? This is false advertizing.
So, there are just 2 examples of how the "performance" excuse (because that's what it is, an excuse) can hurt gameplay and the overall customer experience.
Now, back to my statement:
:...the game already runs like s--- on lots of peoples computers so what's a few fewer FPS if it means a better and more "historically correct" game experience?"
If my performance suffers a bit because the tank in example 1 doesn't disappear but then my team goes on to win the round, do you think I'm worrying about my frame rate dropping from 30 FPS to 25 FPS?
NO.
And If I can actually tell which squad leader is speaking or giving a noticeable visual cue that is warning me of danger or giving out instructions that help my team win the round, do you think I'm worried that hit to the frame rate for the 10 seconds the avatar is "speaking"
NO.
And is there any REAL difference in the game running at 25 FPS as opposed to 30 FPS?
NO.
And do I get odd changes in performance across ALL maps each time there is a game update anyway? Changes in performance that swing wildly in either direction?
YES.
And has anyone EVER come into this forum and complained about some existing "psychologically realistic' feature of the game that should be removed because it hurt their frame rate?
I can't swear to it but I don't think so.
So when I hear the excuse that adding or including a feature will "hurt performance" to the detriment of the player's experience, I'm calling BS.