It all probably started with Anton Checkov's famous quote, "Don't tell me the moon is shining; show me the glint of light on broken glass." A great idea that seems to have got out of hand!
And yet, trying to show everything in your writing can be exhausting, and can lead to painfully obtuse prose. Maybe you don't want every scene to be a riddle, and every character's emotions to be a mystery. You're not wrong in this. It is often the case that if you want your reader to know something, you have to tell them. Don't avoid this because of that tired mantra, “show, don't tell.”
Likewise, since Ernest Hemingway declared war on adverbs, passive voice and long words, more red ink has been spilled on manuscripts than blood sucked by vampires (the cool ones - those running around spouting poetry through perfect mouths with full sets of teeth). There is even a Hemingway app to check how well-written your manuscript is.
Interestingly enough, someone actually copied an excerpt by Hemingway and tried it out. And you know what? They scored an average score. The master himself, it turns out, used adverbs. And long words. And (gasp) passive voice!
What does that tell us? Simple: Showing instead of telling and avoiding adverbs, passive voice and long words are techniques, not writing dogma. They have become an adage because they so often apply to mismanaged writing. Writers can want their readers to know something so badly, they beat it into the ground. This forces sentiments and steals the experience of the story from the reader. You have to maintain a balance. The nature of that balance is up to you.