YOU SAID:
I really like cats but not kittens
INTO JAPANESE
私は本当に猫が好きですが、子猫は好きではありません
BACK INTO ENGLISH
I really like cats, but I do not like kitten
INTO JAPANESE
私は本当に猫が好きですが、私は子猫が好きではありません
it is unlikely that this phrase will ever reach equilibrium