In English, the phrase I was going for was “I would think”. It’s correct in English, and means mostly the same thing as “I think”, with slightly different connotations. I’m not exactly sure how to verbalise what those connotations are, just that in this case it felt better. I think in this context it made it slightly more comical/sardonic?
Obviously, “je croirais” is the correct literal translation of “I would think”. But does it not work to carry a similar connotation in French? And if not, is there some other phrase/conjugation of croire I could use to get across that tone?
Unfortunately my French knowledge is almost entirely academic, so knowing how to use it with more nuance than literal word-for-word changes is a bit beyond me, outside of where that is obviously academically inappropriate.