Oh I'm with you on show not tell (besides obvious literal things like control prompts), my suggestion was more about simplifying each stage in the first part of a jam game so the player has to demonstrate a grasp on one specific game mechanic at a time to move on. I do like the progression of hazards in your levels, and tbf I think if it had checkpoints in each level that would show a lot more, bc a lot of the not-learning came from the fact that you'd have to repeat a large chunk of game you already know before getting back to where you were, and I'd always be inconsistent with how much health I had when I did get back so sometimes it felt out of my power and created a lame duck situation half the times I got back to the part I was stuck at. Tbh now that I type that out loud the problem might be more that you have two independent health bars in a long gameplay stretch, and the fact that one of them drains over time can contradict with how you have to be meticulous about killing everything or tackling tricky platform sections.
Since the health bars thing is a more long-form mechanic and not exactly something you'd showcase in one stage maybe my spiel about level design wasn't the best comparison. The best course of action (I mean besides checkpoints) might have been to focus more on giving the player more feedback about it (it took me a while to really grasp the health bars), or just condensing it to one health pool and maybe ditching the losing it over time thing. Burning the scenery for health was one of the most satisfying parts, but after finding out it was just to maintain a separate health bar it felt more like an obligation. Maybe the dots could've been a special bar instead that you could use for something proactive. Or a thin layer of armor that prevents you from losing health once or twice before you have to recharge it by burning more stuff. Or maybe the ghost mechanic could've drained from it, so more things burned means more time to resurrect. If that second health bar had some benefit to it I think that could've added a helpful extra layer to the gameplay imo, or at least I'm just spitballing here.
Also the ghost mechanic didn't seem to really work a lot of the time when I killed stuff so the threshold was kind of unclear? So put that under the feedback part I guess.