It's arguably a waste of time to respond, but okay:
Not quite; even in the very first Zelda game, the triforce was distinguished into three separate sections, one conveying Wisdom (held by Zelda), one conveying Power (held by Ganon), and one conveying Courage (held by Link).
From the very outset, the entire reason the triforce is designed as three threes is that it represents three distinct characteristics, corresponding to the three main characters.
That is theme.
First, the Triforce of Courage didn't come into being until the second game. But more importantly, everything you've said, while true, tells us more about characters than themes. Otherwise, I could write a story where Bob seeks the Rectangle of Courage, while Bill receives the Pentagon of Love, while Sarah seeks out the Hexagon of Honesty, and claim that this represents a theme. If I play my cards right, it might tell the reader something about the characters (certainly Digimon pulled it off), but as a "theme?" Not really.
And even then, back to the original point of iconography representing theme. Even sticking with LoZ, take the Light Force. It looks the same as the Triforce, but it isn't, and there's no real deeper theme to it in Minish Cap. As iconography, it's recognizable, but that's it - iconography.
Themes and motifs are basic building blocks. Whether they are well developed or not is another question. In all levels of education, they will focus on texts that convey themes effectively, to teach you comprehensive skills and understanding.
Your argument here is a little like saying, "Oh, well if everything has words in it, then nothing does!"
Difference is that words are even more basic/more foundational. It's literally impossible to write a story without words unless you're writing in binary or something (let's avoid the semantics, please?) Difference is that theme is a more abstract concept.
Entertaining the idea that you're correct, that everything has a theme, then maybe you can draw parallels, but even if this is true, words are more foundational than themes.
You've mistaken levels of sophistication with the use of basic elements.
Per above, I disagree that theme is a basic element.
I'd argue that the most basic element of a story is plot, because without plot, you don't have a story by definition. Theme, by contrast, to use a metaphor I've often used, is the frosting on the cake - great to have, but not required, and not foundational. I might have a great theme, but if I don't have solid plot/characters/storytelling, it'll ring hollow, except in exceptional circumstances (e.g. 2001: A Space Odyssey has weak characters sans Hal, but strong theme).