Not sure about English, but in Italian the difference would be, roughly:
Humanist: it belongs to humanism.
Humanistic: it refers to humanism.

As far as I know, humans are responsible for 100% of the fonts in existence. But they are selling paintings done by Elephants now...

If in doubt, prefer the word with fewer letters.

"human" and "humanist" are cognates, obviously, but they are not equivalent.

If in doubt, prefer the word with fewer letters.

Sound advice!