Kakashi has reached the maximum he can get.His stamina, im certain that is plot no jutsu because of the war, but still that isnt getting stronger. Obviously he can continue copying low rank techniques but thats about it
Sorry but this is a baseless statement.How Kakashi reached his maximum when he's getting better after each fights?
Low rank jutsus?It seems that you doesn't know sharingan abilities very well.He can even copy A rank jutsu which is high rank like rasengan or Daibakufu no Jutsu .
Sharingan can copy ninjutsu,genjutsu and taijutsu which helps to get stronger.
Your statements to say that Kakashi isn't getting better is wrong and baseless.
About stanima plot no jutsu? lol so since the beginning of manga it's plot no jutsu when he was exhausted and couldn't fight with sharingan after used only 2 suiton jutsus?
If you pay attention,you'll notice that since the begining of manga, after each fight Kakashi shows a better endurance.