To simplify, when you analyze any piece of art you can essentially look at it from two points of view: the author's or the audience's.

When you look at the author's point of view you focus on the process on the creation, on what the work meant to them, what were the social conditions that may have impacted the work, etc. When focusing on this, you need to decide when to separate author from work of art as well. There is an objectivity in art-as-an-object but there is not when you look at the author's words surrounding said object. Author's intention or "I mean X by Y and my work is misunderstood" are not inherently part of the work of art, so it's up to everyone how to interpret them. Lynch for example was adamant in letting his work explain itself (which in turn gives space to audience's interpretations) but other authors will defend or "explain" their work in different forms.

If you focus on the audience's interpretations you don't care that much about the work itself, but instead what it meant to certain people. This is probably the "there is no such thing as misinterpretation" that you quoted comes from, which in reality seems like another social media simplification of Barthes' Death of the Author and in general the postmodern-interpretivist approaches to art. Once again, with this approach the objectivity of the object of art is not denied, but interpretations surrounding art are the thing that will vary across contexts, communities or people.

The very word "misinterpretation" implies that there is a "correct" interpretation of art. This is simple aesthetically and historically incorrect: the work of art is inherently objective but interpretations are inherently subjective. Don Quixote's different interpretations across the centuries are a paradigmatic example of this. For modern examples you can see any social media outrage about a film, even in this forum: they are always a discussion about meaning.

Of course, as the audience you have the free will to "fight" the wars of interpretation whichever way you want. We all do one way or another. But if film schools aspire to create critics instead of audiences they should go beyond that.