"but after I watched it, I felt nothing."
Honestly I have to agree with your editor: why not explore that?
I don't want to make anhedonia and depression contagious, nor do I want to be boring.
Do you really attribute your feelings about this episode to depression and/or anhedonia? What differentiates it from episodes which you don't feel this way about? Can you quantify that?
One of the easiest ways to explain something in a relatable way is to provide shared context. Even if you and your audience ultimately disagree about how you feel about the context you use, even if your audience feels differently about the episode in question as well, it provides a basis of comparison for that audience which offers useful insight into your own feelings and thoughts. That's easily something interesting to read about: how someone else experienced something differently, in a way that is thoughtfully presented with points of reference and explanation and exploration that make it more than just an arbitrary statement of differing opinion.
The episode made you feel nothing: how does that make you feel?
You spent however long (30 minutes? an hour?) watching a TV show, and came out with this flat affect in regards to it. Take one step back: how do you feel about being left with that lack of feeling as an outcome of your time spent watching? How does that make you feel about the decisions that presumably went into making the show? Would you rather this episode just not exist? What does a holistic view of this episode in the broader series make you feel, contexted specifically to this episode rather than as a review of the show overall?
Hyperbole And A Half (hyperboleandahalf.blogspot.com/2013/05/depression-part-two.html ) did a great job with it, but her style is the exact opposite of mine.
Her style might be the opposite of yours (and involve use of cartoon imagery) but I think there's room here for you to explore things in a similar conceptual manner: step away from the episode and explore your experience of the episode. Does this mirror similar patterns you've come across in other shows? Do you have similar feelings about those?
What if you take yet another step back?
If there's not enough to write about here directly, don't be afraid to explore meta-aspects/topics
Whether in relation to yourself or in relation to the show or in relation to similar shows or simply TV/video in general, there's plenty of ways to make this relatable. To me, it absolutely seems like your editor was giving you a green light to explore more your own feelings in relation to this episode rather than simply the episode itself specifically. And, really... isn't that more interesting as a reader?
Your audience has all (presumably) watched the same episode, unless this anthology is meant to be nothing more than an episode synopsis. Anyone can summarize a book or show, there are plenty of places to go for things like plot summaries; people read something like an anthology of essays regarding a show for something more, something that goes beyond mere summary. A viable approach for that is to give them yourself, in relation to this episode, to whatever extent you're comfortable doing so.
One way to do this would be to roll in some personal anecdotes, then relate them back to not this episode's contents, but rather your lack of feeling that was evoked while watching it (you can for example start them seemingly non sequitor, in medias res, and then reel them back in to how they are relevant).
Even something that leaves you feeling flat in the moment, in direct relation, has room for emotion as a consequence of that, has room for related topics which themselves unbundle emotion, and room for rapport with your audience in relation to your experience: none of that sounds very flat as something to read. Instead it sounds like some of the better pieces I've read in relation to things like shows and books, the ones that developed aspects of personally relatable consequence to the act of experiencing the piece being written about. Sometimes to the point where I'm left fairly sure that the piece being written about couldn't compare to what the piece that used it for inspiration and sometimes little more than a rough framing turned out to be.