I enjoy discussing intellectual topics sometimes and I can hold my own in this kind of conversation, but in general I prefer to talk about more personal things like music, hobbies, plans for the future, etc. I prefer to discuss people and their interests than to have disconnected, objective debates about scholarly topics. However if you can make the topic more personal then I'm more likely to be engaged. For example, a conversation about Einstein's contributions to science = a potentially boring lecture; a conversation about how Einstein's discoveries intersected with personal events in his life = interesting. INFPs are interested in things like science, politics, religion, philosophy, etc. - we just want to hear the human side of it. How does it affect us as people? Maybe you just need to present these topics in a way that appeals to them more (or find INFPs with a passion for the scholarly topic of your choosing because we are super passionate and if we're interested in something we probably know 110% of what there is to know about it).
(Just as an aside, my dad is a high school teacher in NYC and when the time comes for Regents exams (annoying high school level standardized tests in every major subject that only exist in NY state) my dad always encourages his students to guess on MC questions because "even the drunk chicken will guess right 25% of the time" (his words). Obviously that doesn't mean the drunk chicken actually knows 25% of the material being covered on the test. Why should we assume that because a student gets a 75 on an exam it means that student knows 75% of the material? Maybe they only know 60% and they're a very lucky guesser. Or maybe they know 90% but had an off day, or there was an unusually high number of questions on the 10% they didn't know.)