Like you, I thought the “-istic” suffix was superfluous but when I checked it out, it forms ‘adjectives from nouns or from other adjectives, with the meaning "o

Like you, I thought the “-istic” suffix was superfluous but when I checked it out, it forms ‘adjectives from nouns or from other adjectives, with the meaning "of or pertaining to" the preceding component’¹. In this case, “capitalist” could be either a noun or an adjective while “capitalistic” is unambiguously an adjective. I tend to use “capitalist” as an adjective (pertaining to “capitalism”) as it’s usually clear from the context that the word is an adjective. However, it’s not wrong to use “capitalistic” and I’d say it’s a matter of personal style rather than grammar. https://en.wiktionary.org/wiki/-istic#English https://en.wiktionary.org/wiki/-istic#English